Both of mine at night. DD - first contraction around 10pm, waters didn't break until around 4pm (very slow ramp up!!), DD born 5.45am. Loooong labour!

With DS, first contraction 3am, waters broke 8am, DS born 9.20am.

Nice and quick

Apparently the hormones that start labour are strongest at night, so most women go into labour at night!