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Currently we implement adding units larger than `.day` as follows: - Convert the date to date components - Update the value of the added component - Convert the date components back to date The time of the day information is reduced to a `DateComponents` with, e.g. `hour == 1`, `minute == 30`, at step 1. Then when we convert the `DateComponents` back to `Date` at step 3, we always use the *first* occurrence of the time if it falls into the DST repeated time frame. This is different from `Calendar_ICU`'s implementation, which uses the *latter* and rewind back the date by the DST transition interval (e.g. 1 hour for Pacific Time). These yeild the same result except for when the input time and the output time are *both* during DST transition time frame. Update the implementation to match Calendar_ICU's behavior.