linux中日期相关操作需要使用date命令。date帮助文档如下：
[chaoql@localhost c]$ date --help
Usage: date [OPTION]... [+FORMAT]
or: date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
Display the current time in the given FORMAT, or set the system date.
Mandatory arguments to long options are mandatory for short options too.
-d, --date=STRING display time described by STRING, not 'now'
-f, --file=DATEFILE like --date once for each line of DATEFILE
-I[TIMESPEC], --iso-8601[=TIMESPEC] output date/time in ISO 8601 format.
TIMESPEC='date' for date only (the default),
'hours', 'minutes', 'seconds', or 'ns' for date
and time to the indicated precision.
-r, --reference=FILE display the last modification time of FILE
-R, --rfc-2822 output date and time in RFC 2822 format.
Example: Mon, 07 Aug 2006 12:34:56 -0600
--rfc-3339=TIMESPEC output date and time in RFC 3339 format.
TIMESPEC='date', 'seconds', or 'ns' for
date and time to the indicated precision.
Date and time components are separated by
a single space: 2006-08-07 12:34:56-06:00
-s, --set=STRING set time described by STRING
-u, --utc, --universal print or set Coordinated Universal Time (UTC)
--help display this help and exit
--version output version information and exit
FORMAT controls the output. Interpreted sequences are:
%% a literal %
%a locale's abbreviated weekday name (e.g., Sun)
%A locale's full weekday name (e.g., Sunday)
%b locale's abbreviated month name (e.g., Jan)
%B locale's full month name (e.g., January)
%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C century; like %Y, except omit last two digits (e.g., 20)
%d day of month (e.g., 01)
%D date; same as %m/%d/%y
%e day of month, space padded; same as %_d
%F full date; same as %Y-%m-%d
%g last two digits of year of ISO week number (see %G)
%G year of ISO week number (see %V); normally useful only with %V
%h same as %b
%H hour (00..23)
%I hour (01..12)
%j day of year (001..366)
%k hour, space padded ( 0..23); same as %_H
%l hour, space padded ( 1..12); same as %_I
%m month (01..12)
%M minute (00..59)
%n a newline
%N nanoseconds (000000000..999999999)
%p locale's equivalent of either AM or PM; blank if not known
%P like %p, but lower case
%r locale's 12-hour clock time (e.g., 11:11:04 PM)
%R 24-hour hour and minute; same as %H:%M
%s seconds since 1970-01-01 00:00:00 UTC
%S second (00..60)
%t a tab
%T time; same as %H:%M:%S
%u day of week (1..7); 1 is Monday
%U week number of year, with Sunday as first day of week (00..53)
%V ISO week number, with Monday as first day of week (01..53)
%w day of week (0..6); 0 is Sunday
%W week number of year, with Monday as first day of week (00..53)
%x locale's date representation (e.g., 12/31/99)
%X locale's time representation (e.g., 23:13:48)
%y last two digits of year (00..99)
%Y year
%z +hhmm numeric time zone (e.g., -0400)
%:z +hh:mm numeric time zone (e.g., -04:00)
%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z alphabetic time zone abbreviation (e.g., EDT)date命令默认获取当前时间：
[chaoql@localhost c]$ date
Fri Jan 13 12:46:22 CST 2023- 根据帮助文档中的参数格式化时间(date后面的这些参数中间如果没有空格，可以省略双引号)：
[chaoql@localhost c]$ date +"%Y-%m-%d %H-%M-%S"
2023-01-13 12-47-51
[chaoql@localhost c]$ date +%Y-%m-%d_%H-%M-%S
2023-01-13_12-48-05- 使用
%s获取自1970-01-01 00:00:00以来的秒数：
[chaoql@localhost c]$ date +%s
1673585430- 使用
--date参数获取昨天的日期：
[chaoql@localhost c]$ date --date="1 days ago"
Thu Jan 12 12:53:24 CST 2023
[chaoql@localhost c]$ date --date="1 days ago" +%Y-%m-%d
2023-01-12
[chaoql@localhost c]$ date --date="1 days ago" +%Y-%m-%d_%H:%M:%S
2023-01-12_12:53:30- 使用
--date参数指定时间：
[chaoql@localhost ~]$ date --date="2026-01-01 00:00:00"
Wed Jan 1 00:00:00 CST 2026- 使用
--date参数获取2026年2月的天数：
[chaoql@localhost ~]$ date --date="2026-03-01 1 days ago" +%d
29
