The first cell with a surviving lineage to get organised. There could have been countless other 'attempts' that, for one reason or another, failed to get established, or died out before they could leave a trace in the fossil record.
People think of "Tuesday night" as the night that falls at the end of Tuesday, however the majority of it from an astronomy perspective tends to fall after midnight (particularly with daylight savings time), hence it's referred to as the 2nd.