[BugFix] #861
[BugFix] #874.
[Bugfix] Bug #880. Usability: Set "Date mode" regime as default.

Details:
1. Updated datepicker specification (tests).
2. Fixed bug.
Merge pull request #888 from MichaelKalygin/bugfix874

[BugFix] #874.
Merge pull request #890 from alex-zen/bugfix880

[Bugfix] Bug #880. Usability: Set "Date mode" regime as default.
Merge pull request #886 from MichaelKalygin/bugfix861

[BugFix] #861