The BSON spec defines a 'UTC datetime' field, specified as number of milliseconds since the epoch. However, milliseconds is often far too coarse grained for recording timestamps in high performance systems. It is also rather wasteful of the entire 64 bit range. A signed 64 bit integer can represent slightly less than 300 milliion years worth of milliseconds. That is a very long time.

The BSON spec should offer a high resolution UTC datetime type, denominated either in microseconds (almost 300,000 years in an int64_t), or even nanoseconds (still almost 300 years). Perhaps both?