Originally Posted by
AboveAndBeyond
As far as the FAA is concerned, it has to be by flight (FAR 61.51). But, you only need to log time to show proficiency and/or for a rating or certificate. There is no FAA requirement to log every hour flown. Entering flights by day is not FAA authorized, however.
There is no FAA requirement to log time by the individual flight, per leg, per day, hour, minute, week, month, or year. The FAA does not specify how the time must be logged, with respect to a per-flight or per-leg basis. Such a requirement is not found in 14 CFR 61.51.
The only time that is required to be logged is that used to meet the requirements of a certificate, privilege, or rating, and to show recency of experience.
The FAA does not "authorize" logging flights by the day, or not logging flights by the day, because FAA "authorization" is not needed, or relevant. One may log by the hour, by the trip, leg, day, week, month, year, or decade, if one wishes. So long as one meets the legal requirements to establish experience for a certificate, privilege, or rating, or recency of experience, the grouping of one's flights is irrelevant.