Random date time with the year and month hard coded.

RandomDateTime.sql

SELECT '2015-01-'
		+ RIGHT('00' + CAST(
			ROUND(((28 - 1 -1) * RAND() + 1), 0)
		AS varchar), 2)
		+ ' '
		+ RIGHT('00' + CAST(
			ROUND(((24 - 0 -0) * RAND() + 0), 0)
		AS varchar), 2) -- Hour
		+ ':'
		+ RIGHT('00' + CAST(
			ROUND(((59 - 0 -0) * RAND() + 0), 0)
		AS varchar), 2)-- Minute
		+ ':'
		+ RIGHT('00' + CAST(
			ROUND(((59 - 0 -0) * RAND() + 0), 0)
		AS varchar), 2)-- Second
		+ '.'
		+ RIGHT('000' + CAST(
			ROUND(((999 - 0 -0) * RAND() + 0), 0)
		AS varchar), 3)-- Microsecond