starting time of work; opening time
Refers to the time when work or school officially begins for the day.
The starting time of work is 9 o'clock.
I left home early so as not to be late for the start of work.
終業時間 means 'closing time' or 'finishing time of work', the opposite of 始業時間.
始業式 is the opening ceremony at the beginning of a school term, while 始業時間 is the daily start time.
Compound of 始業 (beginning work/school) and 時間 (time).