Angels have a different reckoning of time. To start, read On Time: The Hours from the Ministers of Grace Apocrypha.
The Calendar – This page contains a conversion chart as relative to the Western Gregorian calendar.
The Hours – This page contains conversion charts that list the ruler of the hour as relative to the day.
If there’s a specific date you’d like to have translated into the angels’ time—e.g. your birthday—please leave me a comment on this page.