When the log reaches a specified size
At a specified start-time, start-day, and interval
At a specified start-time, start-day, and interval, if the log file is bigger than a specified size
The start-time, start-day, and interval can have the following combinations:
Time-of-day followed by an interval of days, hours, or minutes
Day-of-week and time-of-day, followed by an interval of weeks
Day-of-month and time-of-day, followed by an interval of months
The time-of-day takes precedence over the interval. For example, a log that is specified to be rotated at 3am and then every 10 hours is rotated at the following times: 03:00, 13:00, 23:00, and again at 03:00 (not 07:00).
If the log is configured for rotation on the 31st of the month but the month has fewer than 31 days, the log is rotated on the first day of the following month.