AWS v4 Signature not working - Error "Invalid date format header"

Hi! I am using Seafile with an s3 compatible service - iDrive e2 - and everything works great with v2 signatures, but if I set use_v4_signature to true then I get “Invalid date format header, expected to be in ISO8601, RFC1123 or RFC1123Z time format” and Seafile cannot access files. What am I missing? v4 is supported by iDrive. Thanks