Use ISO 8601 or RFC 2822 instead of unix timestamp

[IonicaBizau]

It would be good to migrate the unix timestamp dates to IS 8601 or RFC 2822 formats.

git commit --help helps us:

• RFC 2822
  The standard email format as described by RFC 2822, for example Thu, 07 Apr 2005 22:13:13 +0200.
• ISO 8601
  Time and date specified by the ISO 8601 standard, for example 2005-04-07T22:13:13. The parser accepts a space instead of the T character as well.
  Note
  In addition, the date part is accepted in the following formats: YYYY.MM.DD, MM/DD/YYYY and DD.MM.YYYY.