One More Thing: Formatting Dates

Although the NSDateFormatter class has evolved a great deal from its early days and now offers highly customizable elements that can be localized for various calendars and cultures, it helps to have a quick reference on hand for the most common date and time formats. Table 11-1 provides that reference, listing the most commonly used default codes. These codes are like the ones used in Recipe 11-10 to format the results from the date picker’s date property for the midscreen label. Listing 11-1 uses the formats from Table 11-1 to create an NSString utility that converts a string into a date using a format of Month-Day-Year (for example, @"05-22-1934").

Table 11-1. Default Format Codes for the NSDateFormatter Class

Type	Code	Notes
Day of month	d	1 to 31, no leading zeros
	dd	01 to 31, uses leading zeros
Month	M L	1 to 12, numeric month value, no leading zeros
	MM LL	01 to 12, numeric month value, leading zeros
	MMM LLL	Jan to Dec, three-letter month abbreviation
	MMMM LLLL	January to December, full month name
Year	y u	Four-digit year (e.g., 2009)
	yy	Two-digit year (e.g., 09)
Hour	h K	1 to 12, no leading zeros
	hh KK	01 to 12, leading zeros
	H k	0 to 23, 24-hour clock, no leading zeros
	HH kk	00 to 23, 24-hour clock, leading zeros
Minutes	m	0 to 59, no leading zeros
	mm	00 to 59, leading zeros
Seconds	s	0 to 59, no leading zeros
	ss	0 to 59, leading zeros
AM/PM	a
Day of Week	ccc EEE	Sun through Sat, three-letter abbreviations
	cccc EEEE	Sunday through Saturday, full names
	c e	Ordinal day of week (0–7)
	cc ee	Ordinal day of week (00–07)
Week of Month	F	1–5, no leading zeros
	FF	01–05, leading zeros
Day of Year	D	1–366, no leading zeros
	DD	01–366, one leading zero
	DDD	001–366, two leading zeros
Week of Year	w	1–52, no leading zeros
	ww	01-51, one leading zero
Millisecond of Day	A	0–86399999, no padding
Astronomical Julian Day Number	g	Number of days since 1 January 4713 BCE
Era	G	BC, AD—Christian year notation
	GGGG	Before Christ, Anno Domini—Christian year notation
Quarter	q Q	1–4, quarter of year
	qq QQ	01–04, one leading zero
	qqq QQQ	Q1, Q2, Q3, Q4
	qqqq QQQQ	1st quarter, 2nd quarter, 3rd quarter, 4th quarter
Time Zone	v	Two-letter time zone (e.g., MT)
	V z	Three-letter time zone (e.g., MDT)
	vv VV ZZZZ	RFC 822 time zone offset from Greenwich Mean Time (e.g., GMT-06:00)
	vvvv	Time zone name (e.g., Mountain Time)
	VVVV	Time zone location (e.g., United States [Denver])
	zzzz	Full time zone name (e.g., Mountain Daylight Time)
	Z	GMT offset (e.g., -0600)
Other characters	: - /	Colon, hyphen, slash