Strengthening program time (Ja: 強化プログラムタイム, Rom.: Kyōka Puroguramu Taimu) is a mechanic of the game whereby playing songs within certain time periods can give the player bonus rewards in addition to the standard ones.
Every day, you advance one day on the schedule (i.e. if your Monday is day B, Tuesday will be day C). Players are not all on the same day of the schedule (it's determined based on user ID).
As the name suggests, the bonus rewards during strengthening program time are the strengthening items. These are items which can be used instead of other members when performing lessons.