What do swallows say in July?

Yan can't come on March 3rd, nor can he go on September 9th.

The swallows in July are in the north, and there is a saying in Beijing that swallows don't come until March 3, and they don't go until September 9. The third day of March mentioned here is the third day of the lunar calendar, just before and after Tomb-Sweeping Day.

Yan is small, with a body length of 130 to 180 mm, a small and sharp mouth, a large jaw, thin wings and long forked wings at the tail.