It's all in the trigger squeeze.
Galactic Standard Calendar
The Galactic Standard Calendar is a time standard set by Coruscant – Imperial Center.
Coruscant has 10 months consisting of 35 days a month and 24 hours in a day.
The Calendar was reset after the Battle of Yavin to ABY 0-0-0. (ABY=After Battle of Yavin).
The first number is the year, the second is the month (out of 10) and the third is the day (out of 35).
The campaign starts on ABY 0-4-1. The same year as the battle of Yavin, in the fourth month and on the 1st day.