Just to add some random thoughts: this specific thing can be done easily enough without a dependency if your needs are very simple ->
DateTime.to_unix(DateTime.utc_now()) + 60*60
... but yeah, just use Timex Dates and times are amazingly difficult to get Right(tm) when you are dealing with timezones, quirks like daylight savings, need better-than-second resolution etc. If you need a simple timestamp in a single arbitrary timezone where a second here or there doesn't particularly matter, not a big deal. If you need anything remotely more than that, use the libraries available.