add function for converting to 12 hour time

2 files changed, 20 insertions, 0 deletions

diff --git a/watch-library/shared/watch/watch_utility.c b/watch-library/shared/watch/watch_utility.c
index 835076d9..dd11c0eb 100644
--- a/watch-library/shared/watch/watch_utility.c
+++ b/watch-library/shared/watch/watch_utility.c
@@ -151,6 +151,13 @@ watch_date_time watch_utility_date_time_convert_zone(watch_date_time date_time,
     return watch_utility_date_time_from_unix_time(timestamp, destination_utc_offset);
 }
 
+bool watch_utility_convert_to_12_hour(watch_date_time *date_time) {
+    bool is_pm = date_time->unit.hour > 11;
+    date_time->unit.hour %= 12;
+    if (date_time->unit.hour == 0) date_time->unit.hour = 12;
+    return is_pm;
+}
+
 float watch_utility_thermistor_temperature(uint16_t value, bool highside, float b_coefficient, float nominal_temperature, float nominal_resistance, float series_resistance) {
     float reading = (float)value;
 
diff --git a/watch-library/shared/watch/watch_utility.h b/watch-library/shared/watch/watch_utility.h
index 66af6ed5..dc0ebb6a 100644
--- a/watch-library/shared/watch/watch_utility.h
+++ b/watch-library/shared/watch/watch_utility.h
@@ -70,6 +70,19 @@ uint32_t watch_utility_date_time_to_unix_time(watch_date_time date_time, uint32_
   */
 watch_date_time watch_utility_date_time_from_unix_time(uint32_t timestamp, uint32_t utc_offset);
 
+/** @brief Converts a watch_date_time for 12-hour display.
+  * @param date_time A pointer to the watch_date_time that you wish to convert for display. Note that this
+  *                  function will OVERWRITE the original date/time, rendering it invalid for date/time
+  *                  calculations. Midnight (hour 0) will become 12, and hours in the afternoon will wrap
+  *                  back around to values from 1-11.
+  * @return True if the value is in the afternoon. You can use this value to determine whether to set the
+  *         PM indicator on the LCD.
+  * @note This function sort of abuses the watch_date_time struct; the date/time that results from calling
+  *       this function is clamped to the hours of 1:00:00 AM through 12:59:59 PM. It no longer reflects a
+  *       valid watch_date_time for writing to an RTC register.
+  */
+bool watch_utility_convert_to_12_hour(watch_date_time *date_time);
+
 /** @brief Converts a time from a given time zone to another time zone.
   * @param date_time The watch_date_time that you wish to convert
   * @param origin_utc_offset The number of seconds from UTC in the origin time zone