Conversion of timestamp from epoch format to datetime

[gautamvij]

Requirement

Support to read data from nginx logs which has timestamp in format 1564388230.097.

Approach

We can include unit param to read epoch time here as defined here

Can you help me with any other approach if this is not suitable ? or else will give the PR.

[andrewgross]

Sounds great, I think it would be reasonable add a date_unit kwarg. Should we use it only if date_format is empty? Or are there occasions where pd.to_datetime would want unit and format?