Package smjg.libs.util.datetimeformat

Date and time formatting. More...

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Detailed Description

Date and time formatting.

The smjg.libs.util.datetimeformat module implements the generation of formatted date and time strings.

Usually, one will not use this module directly, but instead use the corresponding properties of the types defined in smjg.libs.util.datetime.

Format specifiers

The letters of the basic Latin alphabet are reserved for format specifiers.  Each specifier is a letter, or two or more of the same letter consecutively.  The letter denotes what piece of information to format, and the capitalisation and length denote how to format it.  Where alternative capitalisations are given for a single format, they denote the output capitalisation of the corresponding datum.

Letter	Datum	Specifier	Format
Y	Year	yy	Two digits
		yyy	Exact required length
		yyyy	Four digits (longer if necessary)
		YYY	Astronomical notation (BC represented as negative numbers)
B	BC/AD	B or b	BC if necessary
		BB or bb	BC or AD
		BBB or bbb	BCE or CE
		BBBB or bbbb	BCE if necessary
M	Month	m	numeric without leading zero
		mm	numeric with leading zero
		MMM, Mmm or mmm	abbreviated name
		MMMM, Mmmm or mmmm	full name
D	Day of month	d	no leading zero
		dd	leading zero
T	Ordinal suffix	T or t	Ordinal suffix (TH, ND or RD) of last formatted datum
W	Day of week	WWW, Www or www	abbreviated name
		WWWW, Wwww or wwww	full name
H	Hour	H	24-hour without leading zero
		HH	24-hour with leading zero
		h	12-hour without leading zero
		hh	12-hour with leading zero
A	AM/PM	A or a	A or P
		AA or aa	AM or PM
I	Minute	i	no leading zero
		ii	leading zero
S	Second	s	no leading zero
		ss	leading zero
F	Fraction of a second	f	deciseconds
		FF	centiseconds with leading zero
		ff	centiseconds without leading zero
		FFF	milliseconds with leading zero
		fff	milliseconds without leading zero
Z	Time zone	zzzz	offset from UTC

Examples

Format string	Sample formatted date/time
dd/mm/yy	08/09/05
Www dt Mmm yyyy BB	Thu 8th Sep 2005 AD
h:ii AA	4:51 PM
yyyy-mm-dd HH:ii:ss zzzz	2005-09-08 16:51:09 +0100

Literals

Any non-alphabetic character that doesn't have a special meaning is a literal, i.e. it will be placed as is in the generated string.  You can literalise a single character by placing a backquote (`) immediately before it, or any number of consecutive characters by enclosing them in single quotes ('...').

All letters of the basic Latin alphabet, even those that are not defined as format specifiers, must be literalised if they are to occur as are in the generated string.  This is to prevent accidental use of letters that may become format specifiers in future versions of the notation.

The following characters will always be literals: - : , . / space and all Unicode codepoints beyond U+007F.

Alignment fields (since 0.5)

Square brackets ([ ]) can be used to create fields.  A field is a piece of formatting that is padded to a specific width.  Inside a pair of square brackets, the input consists of up to three parts: the left padding, content and right padding.  Either padding part consists of the same literal character one or more times in succession.  The total number of padding characters determines the width of the field.  The field alignment is determined by which paddings are present:

• If there is only right padding, it will be left aligned.
• If there is only left padding, it will be right aligned.
• If there is padding on both sides, it will be centred.  If the content cannot be centred exactly, then the output will have one more padding character on the left, unless in the format string the right padding is longer than the left padding, in which case there will be one more padding character on the right.

An alternative is to place a number just inside the square bracket, next to a single padding character.  Then the number is the field width.  For left-aligned and right-aligned fields, the number must be on the same side as the padding character.  For centred fields, the padding character is given on each side, and the side on which the number is placed will receive the extra padding character if the content cannot be centred exactly.

In the unlikely event that you may wish to use a digit as a padding character, it must be literalised.

Examples

[------Wwww.....]

This is a centred, eleven-character field containing the name of the day of the week.  The generated string will be one of these:

---Sunday..
---Monday..
--Tuesday..
-Wednesday.
--Thursday.
---Friday..
--Saturday.

The format string [11-Wwww.] has the same meaning.

The content can contain any number of format specifiers and literals. For example:

[d/m/yyy           ]HH:ii:ss

creates, if outputting a list of date/time values, a column for the date and a column for the time.  Sample output:

24/9/1979  03:05:42
15/11/1983 21:43:05
3/4/991    13:57:24

Collapsible portions

Curly brackets ({ }) can be used to create a collapsible portion.  This is a portion that will appear in the output only if at least one of the format specifiers within it actually generates something.  Under the current spec, the only conditions in which a format specifier may generate nothing are:

• The B, b, BBBB or bbbb specifier is used, and the date is AD.
• The requested component (or a component required to calculate what is requested) is unspecified in the date/time object being formatted.
• The time zone is not output for any date/time object in which the hour is unspecified.

Examples

d Mmm yyy{ B}{ HH:ii:ss zzzz}

Formats the date, and the time if present, with only one space between them whether the date is BC or AD.

{d }{Mmm }yyy BB

For applications in which an exact date, the month and year or just the year may be known, to prevent leading spaces.

HH:ii{:ss}{.FFF}

For applications in which a time is always known to the precision of minutes, but may sometimes be known more precisely.

See also:

the original proposal (includes discussion)

Since:

0.02

Todo:

Implement timezone TLAs.

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