The Star Date is a method of time-keeping. The numbers represent the year, the month, the week, and the day, in that order and each separated by a period.
For example, Star Date 4300.1.1.1 would be the first day, of the first week, of the first month, of the year 4300.
A year has 12 months, 48 weeks, or 336 days.
A month has 4 weeks or 28 days.
A week has 7 days.
A day is a standard 24-hour Earth day.