When converting datetime to GMT or UTC result gets 21seconds added

[ThePasko]

When converting a specific datetime value to GMT or UTC the output is a bit confusing:
moment.tz("1751-01-01T00:00:00", "Europe/Dublin").clone().tz("Europe/London").format("YYYY-MM-DDTHH:mm:ss.SSSS") -> "1751-01-01T00:25:21.0000"
or this
moment.tz("1751-01-01T00:00:00", "Europe/Dublin").clone().utc().format("YYYY-MM-DDTHH:mm:ss.SSSS") -> "1751-01-01T00:25:21.0000"

The first thing I learned here is that the 25min added is actually not a bug :)
But what about the extra 21 seconds added in both cases?? Is that a bug?

[maggiepint]

It appears that the Europe/Dublin timezone did indeed have a -00:25:21 offset from August 2nd 1880 to October 1st 1916.
Search for Europe/Dublin in the following file:
ftp://ftp.iana.org/tz/data/europe

I realize that your time range predates this. I think there may be something going on with how far back the IANA data goes in Moment-timezone.

If you were to re-post this issue in the moment-timezone repository instead of in the moment repository, @timrwood would get around to looking at it.

[ThePasko]

Thanks!
I reposted in moment-timezone repository moment/moment-timezone#308