February has 28 days (most of the time). There are seven days in a week, and 28 days takes up exactly four weeks. This February’s calendar starts on Sunday, and ends on the Saturday of the fourth week.
This is the only case where a standard calendar takes only four lines (click on the calendar to enlarge):
This doesn’t happen very often. The past time was in 2009. It won’t happen again until 2026. If you like, you can save this year’s calendar until then.