Getting "Validation failed: Remote assertion must match local assertion" errors when generating badge through code

[sampath06]

I am trying to generate the badge programatically using Play Framework and Scala. I am getting this error on both bakery and in the openbadges js api. I have seen that hardcoding issuedOn to a string instead of calculating it seems to work.
I have tried both the options below:
val issuedOn = System.currentTimeMillis() / 1000L

val issuedOn: String = new DateTime( DateTimeZone.UTC ).toString

If I put issuedOn = "2018-08-24T17:52:31.568Z", it seems to work.