PHP – 날짜 관련 함수 정리

• time – 현재 시간에 대한 timestamp

time();
>>> 1593597661

• strtotime – 날짜를 문자로 표현, 반환값은 timestamp

strtotime("now"); // 현재

strtotime("+1 day"); // 1일 후

strtotime("+1 week"); // 1주 후

strtotime("+1 month"); // 1달 후

strtotime("+1 hours"); // 1시간 후

strtotime("next Monday"); // 다음주 월요일

strtotime("last Monday"); // 지난주 월요일

• mktime(시, 분, 초, 월, 일, 년)

mktime(0,0,1,1,1,2020);
>>> 1577836801

mktime(0,0,0, date('m'), date('d'), date('Y')-1); // 1년 전

mktime(0,0,0, date('m')-1, date('d'), date('Y')); // 1달 전

mktime(0,0,0, date('m'), date('d')-1, date('Y')); // 1일 전

• date 함수 관련 format

출처 : PHP: DateTime::format – Manual

format character	Description	Example returned values
Day	—	—
d	Day of the month, 2 digits with leading zeros	01 to 31
D	A textual representation of a day, three letters	Mon through Sun
j	Day of the month without leading zeros	1 to 31
l (lowercase ‘L’)	A full textual representation of the day of the week	Sunday through Saturday
N	ISO-8601 numeric representation of the day of the week	1 (for Monday) through 7 (for Sunday)
S	English ordinal suffix for the day of the month, 2 characters	st, nd, rd or th. Works well with j
w	Numeric representation of the day of the week	0 (for Sunday) through 6 (for Saturday)
z	The day of the year (starting from 0)	0 through 365
Week	—	—
W	ISO-8601 week number of year, weeks starting on Monday	Example: 42 (the 42nd week in the year)
Month	—	—
F	A full textual representation of a month, such as January or March	January through December
m	Numeric representation of a month, with leading zeros	01 through 12
M	A short textual representation of a month, three letters	Jan through Dec
n	Numeric representation of a month, without leading zeros	1 through 12
t	Number of days in the given month	28 through 31
Year	—	—
L	Whether it’s a leap year	1 if it is a leap year, 0 otherwise.
o	ISO-8601 week-numbering year. This has the same value as Y, except that if the ISO week number (W) belongs to the previous or next year, that year is used instead.	Examples: 1999 or 2003
Y	A full numeric representation of a year, 4 digits	Examples: 1999 or 2003
y	A two digit representation of a year	Examples: 99 or 03
Time	—	—
a	Lowercase Ante meridiem and Post meridiem	am or pm
A	Uppercase Ante meridiem and Post meridiem	AM or PM
B	Swatch Internet time	000 through 999
g	12-hour format of an hour without leading zeros	1 through 12
G	24-hour format of an hour without leading zeros	0 through 23
h	12-hour format of an hour with leading zeros	01 through 12
H	24-hour format of an hour with leading zeros	00 through 23
i	Minutes with leading zeros	00 to 59
s	Seconds with leading zeros	00 through 59
u	Microseconds. Note that date() will always generate 000000 since it takes an int parameter, whereas DateTime::format() does support microseconds if DateTime was created with microseconds.	Example: 654321
v	Milliseconds. Same note applies as for u.	Example: 654
Timezone	—	—
e	Timezone identifier	Examples: UTC, GMT, Atlantic/Azores
I (capital i)	Whether or not the date is in daylight saving time	1 if Daylight Saving Time, 0 otherwise.
O	Difference to Greenwich time (GMT) without colon between hours and minutes	Example: +0200
P	Difference to Greenwich time (GMT) with colon between hours and minutes	Example: +02:00
p	The same as P, but returns Z instead of +00:00	Example: +02:00
T	Timezone abbreviation, if known; otherwise the GMT offset.	Examples: EST, MDT, +05
Z	Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.	-43200 through 50400
Full Date/Time	—	—
c	ISO 8601 date	2004-02-12T15:19:21+00:00
r	» RFC 2822 formatted date	Example: Thu, 21 Dec 2000 16:01:07 +0200
U	Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)	See also time()