reporting time; clock-in time
The time one is expected to arrive at the workplace and start work.
The reporting time is 9 o'clock.
time one leaves home for work
The time one departs from home to commute to work, rather than the official start time.
My time for leaving home for work in the morning is around 7:30.
退社時間 is the time one leaves the office, while 出勤時間 is the time one arrives at work or leaves home for work.
Compound of 出勤 (going to work) and 時間 (time).