movement: add sunrise/sunset face

6 files changed, 625 insertions, 0 deletions

diff --git a/movement/lib/sunriset/sunriset.c b/movement/lib/sunriset/sunriset.c
new file mode 100644
index 00000000..9126c3bc
--- /dev/null
+++ b/movement/lib/sunriset/sunriset.c
@@ -0,0 +1,326 @@
+/*
+
+SUNRISET.C - computes Sun rise/set times, start/end of twilight, and
+             the length of the day at any date and latitude
+
+Written as DAYLEN.C, 1989-08-16
+
+Modified to SUNRISET.C, 1992-12-01
+
+(c) Paul Schlyter, 1989, 1992
+
+Released to the public domain by Paul Schlyter, December 1992
+
+*/
+
+#include <stdio.h>
+#include <math.h>
+#include "sunriset.h"
+
+
+/* A macro to compute the number of days elapsed since 2000 Jan 0.0 */
+/* (which is equal to 1999 Dec 31, 0h UT)                           */
+
+#define days_since_2000_Jan_0(y,m,d) \
+    (367L*(y)-((7*((y)+(((m)+9)/12)))/4)+((275*(m))/9)+(d)-730530L)
+
+/* Some conversion factors between radians and degrees */
+
+#ifndef PI
+ #define PI        3.1415926535897932384
+#endif
+
+#define RADEG     ( 180.0 / PI )
+#define DEGRAD    ( PI / 180.0 )
+
+/* The trigonometric functions in degrees */
+
+#define sind(x)  sin((x)*DEGRAD)
+#define cosd(x)  cos((x)*DEGRAD)
+#define tand(x)  tan((x)*DEGRAD)
+
+#define atand(x)    (RADEG*atan(x))
+#define asind(x)    (RADEG*asin(x))
+#define acosd(x)    (RADEG*acos(x))
+#define atan2d(y,x) (RADEG*atan2(y,x))
+
+/* The "workhorse" function for sun rise/set times */
+
+int __sunriset__( int year, int month, int day, double lon, double lat,
+                  double altit, int upper_limb, double *trise, double *tset )
+/***************************************************************************/
+/* Note: year,month,date = calendar date, 1801-2099 only.             */
+/*       Eastern longitude positive, Western longitude negative       */
+/*       Northern latitude positive, Southern latitude negative       */
+/*       The longitude value IS critical in this function!            */
+/*       altit = the altitude which the Sun should cross              */
+/*               Set to -35/60 degrees for rise/set, -6 degrees       */
+/*               for civil, -12 degrees for nautical and -18          */
+/*               degrees for astronomical twilight.                   */
+/*         upper_limb: non-zero -> upper limb, zero -> center         */
+/*               Set to non-zero (e.g. 1) when computing rise/set     */
+/*               times, and to zero when computing start/end of       */
+/*               twilight.                                            */
+/*        *rise = where to store the rise time                        */
+/*        *set  = where to store the set  time                        */
+/*                Both times are relative to the specified altitude,  */
+/*                and thus this function can be used to compute       */
+/*                various twilight times, as well as rise/set times   */
+/* Return value:  0 = sun rises/sets this day, times stored at        */
+/*                    *trise and *tset.                               */
+/*               +1 = sun above the specified "horizon" 24 hours.     */
+/*                    *trise set to time when the sun is at south,    */
+/*                    minus 12 hours while *tset is set to the south  */
+/*                    time plus 12 hours. "Day" length = 24 hours     */
+/*               -1 = sun is below the specified "horizon" 24 hours   */
+/*                    "Day" length = 0 hours, *trise and *tset are    */
+/*                    both set to the time when the sun is at south.  */
+/*                                                                    */
+/**********************************************************************/
+{
+      double  d,  /* Days since 2000 Jan 0.0 (negative before) */
+      sr,         /* Solar distance, astronomical units */
+      sRA,        /* Sun's Right Ascension */
+      sdec,       /* Sun's declination */
+      sradius,    /* Sun's apparent radius */
+      t,          /* Diurnal arc */
+      tsouth,     /* Time when Sun is at south */
+      sidtime;    /* Local sidereal time */
+
+      int rc = 0; /* Return cde from function - usually 0 */
+
+      /* Compute d of 12h local mean solar time */
+      d = days_since_2000_Jan_0(year,month,day) + 0.5 - lon/360.0;
+
+      /* Compute the local sidereal time of this moment */
+      sidtime = revolution( GMST0(d) + 180.0 + lon );
+
+      /* Compute Sun's RA, Decl and distance at this moment */
+      sun_RA_dec( d, &sRA, &sdec, &sr );
+
+      /* Compute time when Sun is at south - in hours UT */
+      tsouth = 12.0 - rev180(sidtime - sRA)/15.0;
+
+      /* Compute the Sun's apparent radius in degrees */
+      sradius = 0.2666 / sr;
+
+      /* Do correction to upper limb, if necessary */
+      if ( upper_limb )
+            altit -= sradius;
+
+      /* Compute the diurnal arc that the Sun traverses to reach */
+      /* the specified altitude altit: */
+      {
+            double cost;
+            cost = ( sind(altit) - sind(lat) * sind(sdec) ) /
+                  ( cosd(lat) * cosd(sdec) );
+            if ( cost >= 1.0 )
+                  rc = -1, t = 0.0;       /* Sun always below altit */
+            else if ( cost <= -1.0 )
+                  rc = +1, t = 12.0;      /* Sun always above altit */
+            else
+                  t = acosd(cost)/15.0;   /* The diurnal arc, hours */
+      }
+
+      /* Store rise and set times - in hours UT */
+      *trise = tsouth - t;
+      *tset  = tsouth + t;
+
+      return rc;
+}  /* __sunriset__ */
+
+
+
+/* The "workhorse" function */
+
+
+double __daylen__( int year, int month, int day, double lon, double lat,
+                   double altit, int upper_limb )
+/**********************************************************************/
+/* Note: year,month,date = calendar date, 1801-2099 only.             */
+/*       Eastern longitude positive, Western longitude negative       */
+/*       Northern latitude positive, Southern latitude negative       */
+/*       The longitude value is not critical. Set it to the correct   */
+/*       longitude if you're picky, otherwise set to to, say, 0.0     */
+/*       The latitude however IS critical - be sure to get it correct */
+/*       altit = the altitude which the Sun should cross              */
+/*               Set to -35/60 degrees for rise/set, -6 degrees       */
+/*               for civil, -12 degrees for nautical and -18          */
+/*               degrees for astronomical twilight.                   */
+/*         upper_limb: non-zero -> upper limb, zero -> center         */
+/*               Set to non-zero (e.g. 1) when computing day length   */
+/*               and to zero when computing day+twilight length.      */
+/**********************************************************************/
+{
+      double  d,  /* Days since 2000 Jan 0.0 (negative before) */
+      obl_ecl,    /* Obliquity (inclination) of Earth's axis */
+      sr,         /* Solar distance, astronomical units */
+      slon,       /* True solar longitude */
+      sin_sdecl,  /* Sine of Sun's declination */
+      cos_sdecl,  /* Cosine of Sun's declination */
+      sradius,    /* Sun's apparent radius */
+      t;          /* Diurnal arc */
+
+      /* Compute d of 12h local mean solar time */
+      d = days_since_2000_Jan_0(year,month,day) + 0.5 - lon/360.0;
+
+      /* Compute obliquity of ecliptic (inclination of Earth's axis) */
+      obl_ecl = 23.4393 - 3.563E-7 * d;
+
+      /* Compute Sun's ecliptic longitude and distance */
+      sunpos( d, &slon, &sr );
+
+      /* Compute sine and cosine of Sun's declination */
+      sin_sdecl = sind(obl_ecl) * sind(slon);
+      cos_sdecl = sqrt( 1.0 - sin_sdecl * sin_sdecl );
+
+      /* Compute the Sun's apparent radius, degrees */
+      sradius = 0.2666 / sr;
+
+      /* Do correction to upper limb, if necessary */
+      if ( upper_limb )
+            altit -= sradius;
+
+      /* Compute the diurnal arc that the Sun traverses to reach */
+      /* the specified altitude altit: */
+      {
+            double cost;
+            cost = ( sind(altit) - sind(lat) * sin_sdecl ) /
+                  ( cosd(lat) * cos_sdecl );
+            if ( cost >= 1.0 )
+                  t = 0.0;                      /* Sun always below altit */
+            else if ( cost <= -1.0 )
+                  t = 24.0;                     /* Sun always above altit */
+            else  t = (2.0/15.0) * acosd(cost); /* The diurnal arc, hours */
+      }
+      return t;
+}  /* __daylen__ */
+
+
+/* This function computes the Sun's position at any instant */
+
+void sunpos( double d, double *lon, double *r )
+/******************************************************/
+/* Computes the Sun's ecliptic longitude and distance */
+/* at an instant given in d, number of days since     */
+/* 2000 Jan 0.0.  The Sun's ecliptic latitude is not  */
+/* computed, since it's always very near 0.           */
+/******************************************************/
+{
+      double M,         /* Mean anomaly of the Sun */
+             w,         /* Mean longitude of perihelion */
+                        /* Note: Sun's mean longitude = M + w */
+             e,         /* Eccentricity of Earth's orbit */
+             E,         /* Eccentric anomaly */
+             x, y,      /* x, y coordinates in orbit */
+             v;         /* True anomaly */
+
+      /* Compute mean elements */
+      M = revolution( 356.0470 + 0.9856002585 * d );
+      w = 282.9404 + 4.70935E-5 * d;
+      e = 0.016709 - 1.151E-9 * d;
+
+      /* Compute true longitude and radius vector */
+      E = M + e * RADEG * sind(M) * ( 1.0 + e * cosd(M) );
+            x = cosd(E) - e;
+      y = sqrt( 1.0 - e*e ) * sind(E);
+      *r = sqrt( x*x + y*y );              /* Solar distance */
+      v = atan2d( y, x );                  /* True anomaly */
+      *lon = v + w;                        /* True solar longitude */
+      if ( *lon >= 360.0 )
+            *lon -= 360.0;                   /* Make it 0..360 degrees */
+}
+
+void sun_RA_dec( double d, double *RA, double *dec, double *r )
+/******************************************************/
+/* Computes the Sun's equatorial coordinates RA, Decl */
+/* and also its distance, at an instant given in d,   */
+/* the number of days since 2000 Jan 0.0.             */
+/******************************************************/
+{
+      double lon, obl_ecl, x, y, z;
+
+      /* Compute Sun's ecliptical coordinates */
+      sunpos( d, &lon, r );
+
+      /* Compute ecliptic rectangular coordinates (z=0) */
+      x = *r * cosd(lon);
+      y = *r * sind(lon);
+
+      /* Compute obliquity of ecliptic (inclination of Earth's axis) */
+      obl_ecl = 23.4393 - 3.563E-7 * d;
+
+      /* Convert to equatorial rectangular coordinates - x is unchanged */
+      z = y * sind(obl_ecl);
+      y = y * cosd(obl_ecl);
+
+      /* Convert to spherical coordinates */
+      *RA = atan2d( y, x );
+      *dec = atan2d( z, sqrt(x*x + y*y) );
+
+}  /* sun_RA_dec */
+
+
+/******************************************************************/
+/* This function reduces any angle to within the first revolution */
+/* by subtracting or adding even multiples of 360.0 until the     */
+/* result is >= 0.0 and < 360.0                                   */
+/******************************************************************/
+
+#define INV360    ( 1.0 / 360.0 )
+
+double revolution( double x )
+/*****************************************/
+/* Reduce angle to within 0..360 degrees */
+/*****************************************/
+{
+      return( x - 360.0 * floor( x * INV360 ) );
+}  /* revolution */
+
+double rev180( double x )
+/*********************************************/
+/* Reduce angle to within +180..+180 degrees */
+/*********************************************/
+{
+      return( x - 360.0 * floor( x * INV360 + 0.5 ) );
+}  /* revolution */
+
+
+/*******************************************************************/
+/* This function computes GMST0, the Greenwich Mean Sidereal Time  */
+/* at 0h UT (i.e. the sidereal time at the Greenwhich meridian at  */
+/* 0h UT).  GMST is then the sidereal time at Greenwich at any     */
+/* time of the day.  I've generalized GMST0 as well, and define it */
+/* as:  GMST0 = GMST - UT  --  this allows GMST0 to be computed at */
+/* other times than 0h UT as well.  While this sounds somewhat     */
+/* contradictory, it is very practical:  instead of computing      */
+/* GMST like:                                                      */
+/*                                                                 */
+/*  GMST = (GMST0) + UT * (366.2422/365.2422)                      */
+/*                                                                 */
+/* where (GMST0) is the GMST last time UT was 0 hours, one simply  */
+/* computes:                                                       */
+/*                                                                 */
+/*  GMST = GMST0 + UT                                              */
+/*                                                                 */
+/* where GMST0 is the GMST "at 0h UT" but at the current moment!   */
+/* Defined in this way, GMST0 will increase with about 4 min a     */
+/* day.  It also happens that GMST0 (in degrees, 1 hr = 15 degr)   */
+/* is equal to the Sun's mean longitude plus/minus 180 degrees!    */
+/* (if we neglect aberration, which amounts to 20 seconds of arc   */
+/* or 1.33 seconds of time)                                        */
+/*                                                                 */
+/*******************************************************************/
+
+double GMST0( double d )
+{
+      double sidtim0;
+      /* Sidtime at 0h UT = L (Sun's mean longitude) + 180.0 degr  */
+      /* L = M + w, as defined in sunpos().  Since I'm too lazy to */
+      /* add these numbers, I'll let the C compiler do it for me.  */
+      /* Any decent C compiler will add the constants at compile   */
+      /* time, imposing no runtime or code overhead.               */
+      sidtim0 = revolution( ( 180.0 + 356.0470 + 282.9404 ) +
+                          ( 0.9856002585 + 4.70935E-5 ) * d );
+      return sidtim0;
+}  /* GMST0 */
\ No newline at end of file
diff --git a/movement/lib/sunriset/sunriset.h b/movement/lib/sunriset/sunriset.h
new file mode 100644
index 00000000..f8b97e32
--- /dev/null
+++ b/movement/lib/sunriset/sunriset.h
@@ -0,0 +1,95 @@
+/*
+
+SUNRISET.H - computes Sun rise/set times, start/end of twilight, and
+             the length of the day at any date and latitude
+
+Written as DAYLEN.C, 1989-08-16
+
+Modified to SUNRISET.C, 1992-12-01
+
+(c) Paul Schlyter, 1989, 1992
+
+Released to the public domain by Paul Schlyter, December 1992
+
+*/
+
+#ifndef SUNRISET_H_
+#define SUNRISET_H_
+
+/* Function prototypes */
+
+double __daylen__( int year, int month, int day, double lon, double lat,
+                   double altit, int upper_limb );
+
+int __sunriset__( int year, int month, int day, double lon, double lat,
+                  double altit, int upper_limb, double *rise, double *set );
+
+void sunpos( double d, double *lon, double *r );
+
+void sun_RA_dec( double d, double *RA, double *dec, double *r );
+
+double revolution( double x );
+
+double rev180( double x );
+
+double GMST0( double d );
+
+
+/* Following are some macros around the "workhorse" function __daylen__ */
+/* They mainly fill in the desired values for the reference altitude    */
+/* below the horizon, and also selects whether this altitude should     */
+/* refer to the Sun's center or its upper limb.                         */
+
+
+/* This macro computes the length of the day, from sunrise to sunset. */
+/* Sunrise/set is considered to occur when the Sun's upper limb is    */
+/* 35 arc minutes below the horizon (this accounts for the refraction */
+/* of the Earth's atmosphere).                                        */
+#define day_length(year,month,day,lon,lat)  \
+        __daylen__( year, month, day, lon, lat, -35.0/60.0, 1 )
+
+/* This macro computes the length of the day, including civil twilight. */
+/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
+/* the horizon.                                                         */
+#define day_civil_twilight_length(year,month,day,lon,lat)  \
+        __daylen__( year, month, day, lon, lat, -6.0, 0 )
+
+/* This macro computes the length of the day, incl. nautical twilight.  */
+/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
+/* below the horizon.                                                   */
+#define day_nautical_twilight_length(year,month,day,lon,lat)  \
+        __daylen__( year, month, day, lon, lat, -12.0, 0 )
+
+/* This macro computes the length of the day, incl. astronomical twilight. */
+/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
+/* below the horizon.                                                      */
+#define day_astronomical_twilight_length(year,month,day,lon,lat)  \
+        __daylen__( year, month, day, lon, lat, -18.0, 0 )
+
+
+/* This macro computes times for sunrise/sunset.                      */
+/* Sunrise/set is considered to occur when the Sun's upper limb is    */
+/* 35 arc minutes below the horizon (this accounts for the refraction */
+/* of the Earth's atmosphere).                                        */
+#define sun_rise_set(year,month,day,lon,lat,rise,set)  \
+        __sunriset__( year, month, day, lon, lat, -35.0/60.0, 1, rise, set )
+
+/* This macro computes the start and end times of civil twilight.       */
+/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
+/* the horizon.                                                         */
+#define civil_twilight(year,month,day,lon,lat,start,end)  \
+        __sunriset__( year, month, day, lon, lat, -6.0, 0, start, end )
+
+/* This macro computes the start and end times of nautical twilight.    */
+/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
+/* below the horizon.                                                   */
+#define nautical_twilight(year,month,day,lon,lat,start,end)  \
+        __sunriset__( year, month, day, lon, lat, -12.0, 0, start, end )
+
+/* This macro computes the start and end times of astronomical twilight.   */
+/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
+/* below the horizon.                                                      */
+#define astronomical_twilight(year,month,day,lon,lat,start,end)  \
+        __sunriset__( year, month, day, lon, lat, -18.0, 0, start, end )
+
+#endif // SUNRISET_H_
diff --git a/movement/make/Makefile b/movement/make/Makefile
index 4910b102..00a086d0 100755
--- a/movement/make/Makefile
+++ b/movement/make/Makefile
@@ -17,6 +17,7 @@ INCLUDES += \
   -I../watch_faces/thermistor/ \
   -I../watch_faces/demos/ \
   -I../lib/TOTP-MCU/ \
+  -I../lib/sunriset/ \
 
 # If you add any other source files you wish to compile, add them after ../app.c
 # Note that you will need to add a backslash at the end of any line you wish to continue, i.e.
@@ -27,6 +28,7 @@ INCLUDES += \
 SRCS += \
   ../lib/TOTP-MCU/sha1.c \
   ../lib/TOTP-MCU/TOTP.c \
+  ../lib/sunriset/sunriset.c \
   ../movement.c \
   ../watch_faces/clock/simple_clock_face.c \
   ../watch_faces/clock/world_clock_face.c \
@@ -45,6 +47,7 @@ SRCS += \
   ../watch_faces/complications/day_one_face.c \
   ../watch_faces/complications/stopwatch_face.c \
   ../watch_faces/complications/totp_face.c \
+  ../watch_faces/complications/sunrise_sunset_face.c \
 
 # Leave this line at the bottom of the file; it has all the targets for making your project.
 include $(TOP)/rules.mk
diff --git a/movement/movement_config.h b/movement/movement_config.h
index 7896f050..f1bed942 100644
--- a/movement/movement_config.h
+++ b/movement/movement_config.h
@@ -41,6 +41,7 @@
 #include "lis2dh_logging_face.h"
 #include "demo_face.h"
 #include "hello_there_face.h"
+#include "sunrise_sunset_face.h"
 
 const watch_face_t watch_faces[] = {
     simple_clock_face,
diff --git a/movement/watch_faces/complications/sunrise_sunset_face.c b/movement/watch_faces/complications/sunrise_sunset_face.c
new file mode 100644
index 00000000..035fd2cf
--- /dev/null
+++ b/movement/watch_faces/complications/sunrise_sunset_face.c
@@ -0,0 +1,149 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Joey Castillo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Sunrise/sunset calculations are public domain code by Paul Schlyter, December 1992
+ *
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include "sunrise_sunset_face.h"
+#include "watch.h"
+#include "watch_utility.h"
+#include "sunriset.h"
+
+static void _sunrise_sunset_face_update() {
+    char buf[14];
+    double rise, set, minutes;
+    // TODO: allow user to set location, using London for now.
+    double lat = 51.509865;
+    double lon = -0.118092;
+    // TODO: account for time zone, currently only operates in GMT.
+    watch_date_time date_time = watch_rtc_get_date_time(); // the current date / time
+    watch_date_time scratch_time; // scratchpad, contains different values at different times
+    scratch_time.reg = date_time.reg;
+        
+    for(int i = 0; i < 2; i++) {
+        uint8_t result = sun_rise_set(scratch_time.unit.year + WATCH_RTC_REFERENCE_YEAR, scratch_time.unit.month, scratch_time.unit.day, lon, lat, &rise, &set);
+
+        if (result != 0) {
+            watch_clear_colon();
+            watch_clear_indicator(WATCH_INDICATOR_PM);
+            watch_clear_indicator(WATCH_INDICATOR_24H);
+            sprintf(buf, "%s%d none ", (result == 1) ? "SE" : "rI", scratch_time.unit.day);
+            watch_display_string(buf, 0);
+            return;
+        }
+
+        watch_set_colon();
+        // TODO: account for user's 12H/24H preference
+        watch_set_indicator(WATCH_INDICATOR_24H);
+
+        minutes = 60.0 * fmod(rise, 1);
+        scratch_time.unit.hour = floor(rise);
+        scratch_time.unit.minute = floor(minutes);
+        scratch_time.unit.second = 60.0 * fmod(minutes, 1);
+
+        if (date_time.reg < scratch_time.reg) {
+            // display today's sunrise, it hasn't happened yet
+            sprintf(buf, "rI%2d%2d%02d%02d", scratch_time.unit.day, scratch_time.unit.hour, scratch_time.unit.minute, scratch_time.unit.second);
+            watch_display_string(buf, 0);
+            return;
+        }
+
+        minutes = 60.0 * fmod(set, 1);
+        scratch_time.unit.hour = floor(set);
+        scratch_time.unit.minute = floor(minutes);
+        scratch_time.unit.second = 60.0 * fmod(minutes, 1);
+
+        if (date_time.reg < scratch_time.reg) {
+            // display today's sunset, it hasn't happened yet
+            sprintf(buf, "SE%2d%02d%02d%02d", scratch_time.unit.day, scratch_time.unit.hour, scratch_time.unit.minute, scratch_time.unit.second);
+            watch_display_string(buf, 0);
+            return;
+        }
+
+        // it's after sunset. we need to display sunrise for tomorrow.
+        uint32_t timestamp = watch_utility_date_time_to_unix_time(date_time, 0);
+        timestamp += 86400;
+        scratch_time = watch_utility_date_time_from_unix_time(timestamp, 0);
+    }
+}
+
+void sunrise_sunset_face_setup(movement_settings_t *settings, uint8_t watch_face_index, void ** context_ptr) {
+    (void) settings;
+    (void) watch_face_index;
+    if (*context_ptr == NULL) {
+        *context_ptr = malloc(sizeof(sunrise_sunset_state_t));
+        memset(*context_ptr, 0, sizeof(sunrise_sunset_state_t));
+    }
+}
+
+void sunrise_sunset_face_activate(movement_settings_t *settings, void *context) {
+    (void) settings;
+    sunrise_sunset_state_t *state = (sunrise_sunset_state_t *)context;
+    movement_location_t movement_location = (movement_location_t) watch_get_backup_data(1);
+    state->latitude = movement_location.bit.latitude;
+    state->longitude = movement_location.bit.longitude;
+}
+
+bool sunrise_sunset_face_loop(movement_event_t event, movement_settings_t *settings, void *context) {
+    (void) settings;
+    (void) context;
+
+    switch (event.event_type) {
+        case EVENT_ACTIVATE:
+            break;
+        case EVENT_LOW_ENERGY_UPDATE:
+        case EVENT_TICK:
+            _sunrise_sunset_face_update();
+            break;
+        case EVENT_MODE_BUTTON_UP:
+            movement_move_to_next_face();
+            break;
+        case EVENT_LIGHT_BUTTON_DOWN:
+            movement_illuminate_led();
+            break;
+        case EVENT_LIGHT_BUTTON_UP:
+            break;
+        case EVENT_ALARM_BUTTON_UP:
+            break;
+        case EVENT_ALARM_LONG_PRESS:
+            // TODO: settings mode, to set the user's location.
+            break;
+        case EVENT_TIMEOUT:
+            // TODO: return home if we're on a settings page.
+        default:
+            break;
+    }
+
+    return true;
+}
+
+void sunrise_sunset_face_resign(movement_settings_t *settings, void *context) {
+    (void) settings;
+    (void) context;
+
+    movement_request_tick_frequency(1);
+}
diff --git a/movement/watch_faces/complications/sunrise_sunset_face.h b/movement/watch_faces/complications/sunrise_sunset_face.h
new file mode 100644
index 00000000..625a0fe3
--- /dev/null
+++ b/movement/watch_faces/complications/sunrise_sunset_face.h
@@ -0,0 +1,51 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2022 Joey Castillo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef SUNRISE_SUNSET_FACE_H_
+#define SUNRISE_SUNSET_FACE_H_
+
+#include "movement.h"
+
+// The Day One face is designed to count upwards from the wearer's date of birth. It also functions as an
+// interface for setting the birth date register, which other watch faces can use for various purposes.
+
+typedef struct {
+    uint16_t latitude;
+    uint16_t longitude;
+} sunrise_sunset_state_t;
+
+void sunrise_sunset_face_setup(movement_settings_t *settings, uint8_t watch_face_index, void ** context_ptr);
+void sunrise_sunset_face_activate(movement_settings_t *settings, void *context);
+bool sunrise_sunset_face_loop(movement_event_t event, movement_settings_t *settings, void *context);
+void sunrise_sunset_face_resign(movement_settings_t *settings, void *context);
+
+static const watch_face_t sunrise_sunset_face = {
+    sunrise_sunset_face_setup,
+    sunrise_sunset_face_activate,
+    sunrise_sunset_face_loop,
+    sunrise_sunset_face_resign,
+    NULL
+};
+
+#endif // SUNRISE_SUNSET_FACE_H_