That depends on your calendar. Some calendars average around the same time as the gregorian calendar, but can deviate significantly on shorter time scales (e.g.

That depends on your calendar. Some calendars average around the same time as the gregorian calendar, but can deviate significantly on shorter time scales (e.g. the Hebrew calendar, which uses lunar months and leap months to keep rough track to a solar calendar). Other calendars have more deviation - for instance, the Islamic calendar merely approximates the solar year with moons on a single year timeframe, so it moves about 10-12 days a year and just accepts that in some years, Ramadan will be in winter and in others it will be in summer. Moreover, even our calendar and epoch has changed. Since Jesus pbuh was conceived nine months before he was born, the English used to record the beginning of the year as the 25th March OS before they adopted the Gregorian calendar. Therefore, the 20 March and the 30 March of the same year would have different numbers. (The general public still celebrate new years on the 1 January in this period, which can make dates between new years and lady day ambiguous.) So unless you circuitously define a "calendar year" to mean "the calendar used for measuring compared to C", your statement is false. If you circuitously define it, it is a useless statement which says nothing more than "true statements which can be made about calendar length are true", which is unnecessarily specific while being at the same time redundant.