Remove unneeded datetime convert

Prevent usage of function .fromtimestamp and .fromordinal that can throw exceptions on some platforms, since these functions are based on the platforms C library. These library's can have different valid date and time ranges, this can throw exceptions.

This could fix the: 
```
timestamp out of range for platform time_t
```
Bug some reported. Since now the 2 functions that produce this exception aren't used anymore.

Also the calls are more simple and have less format changes, so it saves cpu time too.