And remember the score is calculated at the time you pull the record. Different CRAs update at different time, so info that might be reporting to TU may not be reporting to EX and EQ. So there really is no set date to look for a score change, it changes to reflect changes in your report.
Your FICO score is really a snapshot of your report at the minute it is pulled. Scores can change hourly or take years to change if there is little or no activity. You can check your score every day but unless you have reason to believe something got better or worse once a month or quarter or at the very least year would be good.