Time slots iterators and helper functions

[iblislin]

• I need a iterator to create continuous time slots in a given interval of a day.
  • e.g. start from 2021/1/1 to 2021/1/10, in each day, I need to create 15m time slots from am 8:45 to pm 1:45.
• Helper functions:
  • Given a timestamp, find the time slots which the timestamp belongs to.