Why does Apple Health nutrition data have no timestamps?

Apple Health nutrition values do carry per-entry timestamps.

Apple Health nutrition values do carry per-entry timestamps. They arrive in the meals array of the nutrition payload, where each meal object has its own timestamp (ISO 8601, microsecond precision), plus name, type (meal category), quantity and a full micros breakdown.

The summary.macros and summary.micros blocks still give you the rolled-up daily totals, so you get both views: per-entry meals and the day summary.

If you are only seeing daily totals, make sure you are reading the meals array (not just summary) and that you are on a recent iOS SDK version. See the Nutrition data model.