admission date; first day
Used for the day someone enters a facility such as a training institute, care home, or prison. Often appears in official contexts.
The admission date is next Monday.
Please remember to bring the necessary documents on the first day.
入学日 is for school enrollment; 入所日 is for non-school facilities like training centers or care homes.
Compound of 入所 (entering a facility) + 日 (day).