#253. Authoring: Exhibit:Timeline: There is no validation for start date and end date fields
Merge branch 'master' of https://github.com/alterm4nn/ChronoZoom into atvalidatefix
#253. Additional commit, improved year validating
Merge branch 'master' of https://github.com/alterm4nn/ChronoZoom into atvalidatefix
Minor update of year validation in datepicker
Merge pull request #256 from alex-zen/atvalidatefix

#253. Authoring: Exhibit:Timeline: There is no validation for start date and end date fields