 		return CUI.DateTime.formatMomentWithBc(mom, @__input_format.input)
 
 	__checkInput: (value) ->
+		@__calendarButton.enable()
+
 		if not CUI.util.isEmpty(value?.trim())
 			mom = @parse(value)
 			if not mom.isValid()
 				return false
+
+			if mom.bc
+				@__calendarButton.disable()
+
 		else
 			@__input_format = @initFormat(@__default_format)
 		return true

			onDataChanged: =>
				@updateCalendar(mom.year(data.year))
			options: =>
				opts = []
				for year in [data.year-20..data.year+20]
					opts.push
						text: ""+year
						value: year

				opts
		).start()

		if @__input_formats[0].clock

					buttons: [
						icon: "left"
						group: "year"
						onClick: =>
							if data.year - 1 < @_min_year
								return

							mom.subtract(1, "years")
							@drawDate(mom)
					,
