USA 401k rollover at year end

[McMike]

If a 401k rollover is initiated from one 401k account to another 401k at a different trustee at the end of the year in December, does it matter if the rollover deposit is not credited by the "new" trustee until January of the following year? (i.e it is done by check and the check is in transit). (It's technically a "transfer" I suppose)

Does this have any impact on the 1040 for either year?