The adjective form of yippee, a yippitty time is a fun and happy time during which you may have said "hooray", "this is great", or indeed "yippee!" in an excitable manner.
First we went to the park and then we had an ice cream and then we had a dance and then made silly faces, and generally had a wonderfully yippitty day,
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12 step recovery jargon referring to someone new who talks about how great life is, now that they're sober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.