RandDateStr generates time in string representation it is done in such way because we wanted to make JSON statement to work but scylla supports only string representation of date in JSON format.

According to the CQL binary protocol, time is an int64 in range [0;86399999999999] https://github.com/apache/cassandra/blob/f5df4b219e063cb24b9cc0c22b6e614506b8d903/doc/native_protocol_v4.spec#L941 An 8 byte two's complement long representing nanoseconds since midnight.

RandTimestamp generates timestamp in nanoseconds Date limit needed to make sure that textual representation of the date is parsable by cql and drivers Currently CQL fails: unable to parse date '95260-10-10T19:09:07.148+0000': marshaling error: Unable to parse timestamp from '95260-10-10t19:09:07.148+0000'" if year is bigger than 9999, same as golang time.Parse.