Use a consistent date time formatting accross the application.

[vesavlad]

Currently there are multiple formats in which the date is expected to be formatted. There should be a unitary approach to store them and avoid having this incosistencies

[wkulesza]

Maybe a good idea to just stick with the most current one. Alternatively, we could use a format which is tipical for selected timezone, or even else, use unix time?

[wkulesza]

Also all prediction accuracy reports don't work as they use incorrect date convention.