Till last month, for me ICICI used to generate bill on 21. But this month it generated on 20.
Some banks generate statement 1 or 2 days before actual date if statement date falls on holiday. Experienced such in Axis two times when bill was generated 2 days and 1 day early.
Seems like ICICI too followed the same as 21 Jan is holiday. So it generated on 20 Jan.