Calendar.TimeZoneDatabase.time_zone_period_from_utc_iso_days
You're seeing just the callback
time_zone_period_from_utc_iso_days
, go back to Calendar.TimeZoneDatabase module for more information.
Specs
time_zone_period_from_utc_iso_days(Calendar.iso_days(), Calendar.time_zone()) :: {:ok, time_zone_period()} | {:error, :time_zone_not_found | :utc_only_time_zone_database}
Time zone period for a point in time in UTC for a specific time zone.
Takes a time zone name and a point in time for UTC and returns a
time_zone_period
for that point in time.