Same for me. All my Rainbow Pulls were shortly after Midnight (+1 GMT) as well.

I combined Volarmis method with the Silver Pot theory.

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I forgot to screenshot Golden Lace. But i got her also shortly after Midnight.

However this method doesn't work all the time...at least for me. My last few pulls in January using this method were horrible.
I guess it's only an increased chance to get something good and nothing guaranteed.