In golang documentation, it is stated that :
These are predefined layouts for use in Time.Format and Time.Parse. The reference time used in the layouts
It is just the numbers 1 2 3 4 5 6 7
1: month (January, Jan, 01, etc)
2: day
3: hour (15 is 3pm on a 24 hour clock)
4: minute
5: second
6: year (2006)
7: timezone (GMT-7 is MST)