The device's local time of day at a moment, in whole seconds since the
device's local midnight: the epoch reading the event clock gave, with the
device's zone offset applied (timezoneOffsetSecondsOf, or the stored
timezoneOffset when the device names no zone) and taken modulo the day
correctly for zones west of UTC. Every renderer of a device-local time of day
reads it through this one function — an epoch modulo 86_400 alone is the UTC
time of day, which is what the app's seconds_since_midnight fields mean on
a device in any other zone.
The device's local time of day at a moment, in whole seconds since the device's local midnight: the epoch reading the event clock gave, with the device's zone offset applied (
timezoneOffsetSecondsOf, or the storedtimezoneOffsetwhen the device names no zone) and taken modulo the day correctly for zones west of UTC. Every renderer of a device-local time of day reads it through this one function — an epoch modulo 86_400 alone is the UTC time of day, which is what the app'sseconds_since_midnightfields mean on a device in any other zone.