Using a date prior to 1970 in REST api call

Summary

calling report with a date prior to 1970 failing via REST api, eror that it is not a valid date/time format

Content

We have made a report that is to be called via rest api with contacts date of birth as one of the filters.

Report works perfectly fine as long as the contact was not born before 1970 (the epoch).

Any call that passes a date prior to this returns:

"Error in POST data: Invalid date/time: 1968-12-23Z is not a valid date/time format, or is outside of the allowed range"

Have tried without adding zulu to the end, have also tried adding timestamp as well as removing all the hyphens. Attempting to pass a direct value also fails as an invalid type specified.