When passing in dates for a user attribute e.g. When the user signed up, or when the user last logged in. Nickelled requires that you send it in as per the default JavaScript UTC timestamp format
"YYYY-MM-DDThh:mm:ssZ"
You can also include fractions of a second
"YYYY-MM-DDThh:mm:ss.sssZ"
Send in the dates UTC Offset: UTC +0 and ending with Z (short for Zulu time)