There are two components to take into account for this question
- the earth rotation rate on itself
- the orbiting period around the sun
A day back then was shorter than today's earth day. The earth was rotating quicker in the past, but its rotating period around the sun didn't change much because of Kepler's law.
I cannot say how it was 5 billion years ago (anyway, did the earth had something you could call a surface to track the day from then?), but you could find data derived from fossils analysis for the last billion years, e.g. here from Nasa's SpaceMath, on how long a day was back then - I realize now the figures below assume the orbiting period of the earth around the sun (~8766 hours) stayed constant over this period of time. This assumption is wrong as explained here - however stating it "has been close to its current value for the last 2-3 billion years", so below figures are an approximation
From which I would roughly interpolate: 600
days earth self-rotation per year full rotation around the sun 2 billion years ago
We are saying here that earth was rotating quicker in the past:
Detailed studies of fossil shells, and the banded deposits in certain sandstones, reveal a much different length of day in past eras! These bands in sedimentation and shell-growth follow the lunar month and have individual bands representing the number of days in a lunar month.
By counting the number of bands, geologists can work out the number of days in a year, and from this the number of hours in a day when the shell was grown, or the deposits put down. The table above shows the results of one of these studies.