CQL DateTime values are used to represent an instant along the timeline, known to at least the year precision, and potentially to the millisecond precision. DateTime values are specified using an at-symbol (@) followed by an ISO-8601 textual representation of the DateTime value:
@2014-01-25
@2014-01-25T14:30:14.559
For DateTime values, timezone may be specified as either UTC time (Z), or as a timezone offset. If no timezone is specified, the timezone of the evaluation request timestamp is used.
Specifically, because DateTime values may be specified to varying levels of precisions, operations such as comparison and duration calculation may result in null, rather than the true or false that would result from the same operation involving fully specified values.