Reformat date and time values


# Required Description
Using two parameters
1 yes A datetime device
2 yes Output format (see below)
Using three parameters
1 yes A datetime string
2 yes Input format (see below)
3 yes Output format (see below)


Input / output

Consider that the flexibility of the function depends on the input. If you input just %H:%M:%S, the DATE_FORMAT can’t output a format like this %Y-%m-%d, because the function didn’t receive any date information. It only received time information. So, DATE_FORMAT can’t be used to exterpolate information that’s not present.

Return value

The function will output the exact format as requested in the last (second or third argument). There are a few things you must consider when working with the DATE_FORMAT function. The types of operators you can use with DATE_FORMAT depends on the output format requested. If you want to compare the output format %c you can only use the IS operator, because the final output will be interpreted as a string value. If you want to compare %H.%M, you will need numeric operators like ==, >, or <, because the output will be evaluated as a number.

Also consider the usage of quotes. The flexibility in which DATE_FORMAT can format date and time values isn’t always accepted by pilight. For example: DATE_FORMAT(datetime, %c) outputs Fri Apr 24 11:35:36 2015 which pilight subsequently can’t handle. If you want to output string like this, use quotes DATE_FORMAT(datetime, "%c"), which will output as "Fri Apr 24 11:35:36 2015".


IF DATE_ADD(datetime, +1 HOUR) == ...
IF DATE_ADD(datetime, -1 DAY) == ...
IF DATE_ADD(2015-12-31, 23:59:59, +1 SECOND) == ...
IF DATE_ADD(datetime, RANDOM(-3, +3) DAY) == ...
IF DATE_FORMAT(DATE_ADD(2015-01-01 21:00:00, RANDOM(0, 120) MINUTE), \"%Y-%m-%d %H:%M:%S\", %H.%M) == ...


DATE_ADD as an argument

When you use DATE_ADD as the first argument, you should consider the return value of DATE_ADD, because that’s what DATE_FORMAT will eventually receive. The output format of DATE_ADD is "%Y-%m-%d %H:%M:%S", so the input format for DATE_FORMAT should be the same.

Formatting characters

Specifier Replaced by Example
%a Abbreviated weekday name [1] Thu
%A Full weekday name [1] Thursday
%b %h Abbreviated month name [1] Aug
%B Full month name [1] August
%c Date and time representation [1] Thu Aug 23 14:55:02 2001
%C Year divided by 100 and truncated to integer (00-99) 20
%d Day of the month, zero-padded (01-31) 23
%D Short MM/DD/YY date, equivalent to %m/%d/%y 08/23/01
%e Day of the month, space-padded (1-31) 23
%F Short YYYY-MM-DD date, equivalent to %Y-%m-%d 2001-08-23
%g Week-based year, last two digits (00-99) 01
%G Week-based year 2001
%g Week-based year 2001
%H Hour in 24h format (00-23) 14
%I Hour in 12h format (01-12) 02
%j Day of the year (001-366) 235
%m Month as a decimal number (01-12) 08
%M Minute (00-59) 55
%n New-line character (‘n’)  
%p AM or PM designation PM
%r 12-hour clock time [1] 02:55:02 pm
%R 24-hour HH:MM time, equivalent to %H:%M 14:55
%S Second (00-61) 02
%t Horizontal-tab character (‘t’)  
%T ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S 14:55:02
%u ISO 8601 weekday as number with Monday as 1 (1-7) 4
%U Week number with the first Sunday as the first day of week one (00-53) 33
%V ISO 8601 week number (01-53) 34
%w Weekday as a decimal number with Sunday as 0 (0-6) 4
%W Week number with the first Monday as the first day of week one (00-53) 34
%x Date representation [1] 08/23/01
%X Time representation [1] 14:55:02
%y Year, last two digits (00-99) 01
%Y Year 2001
ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100)
If timezone cannot be determined, no characters
Timezone name or abbreviation [1]
If timezone cannot be determined, no characters
%% A % sign %

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[1](1, 2, 3, 4, 5, 6, 7, 8, 9) These specifiers are locale-dependent.