date --help
| %% | 一个文字的 % |
| %a | 当前locale 的星期名缩写(例如： 日，代表星期日) |
| %A | 当前locale 的星期名全称 (如：星期日) |
| %b | 当前locale 的月名缩写 (如：一，代表一月) |
| %B | 当前locale 的月名全称 (如：一月) |
| %c | 当前locale 的日期和时间 (如：2005年3月3日 星期四 23:05:25) |
| %C | 世纪；比如 %Y，通常为省略当前年份的后两位数字(例如：20) |
| %d | 按月计的日期(例如：01) |
| %D | 按月计的日期；等于%m/%d/%y |
| %e | 按月计的日期，添加空格，等于%_d |
| %F | 完整日期格式，等价于 %Y-%m-%d |
| %g | ISO-8601 格式年份的最后两位 (参见%G) |
| %G | ISO-8601 格式年份 (参见%V)，一般只和 %V 结合使用 |
| %h | 等于%b |
| %H | 小时(00-23) |
| %I | 小时(00-12) |
| %j | 按年计的日期(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 |
| %q | quarter of year (1..4) |
| %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 | 秒(00-60) |
| %t | 输出制表符 Tab |
| %T | 时间，等于%H:%M:%S |
| %u | 星期，1 代表星期一 |
| %U | 一年中的第几周，以周日为每星期第一天(00-53) |
| %V | ISO-8601 格式规范下的一年中第几周，以周一为每星期第一天(01-53) |
| %w | 一星期中的第几日(0-6)，0 代表周一 |
| %W | 一年中的第几周，以周一为每星期第一天(00-53) |
| %x | 当前locale 下的日期描述 (如：12/31/99) |
| %X | 当前locale 下的时间描述 (如：23:13:48) |
| %y | 年份最后两位数位 (00-99) |
| %Y | 年份 |
| %z +hhmm | 数字时区(例如，-0400) |
| %:z +hh:mm | 数字时区(例如，-04:00) |
| %::z +hh:mm:ss | 数字时区(例如，-04:00:00) |
| %:::z | 数字时区带有必要的精度 (例如，-04，+05:30) |
| %Z | 按字母表排序的时区缩写 (例如，EDT) |
http://www.cplusplus.com/reference/ctime/strftime/
| specifier | Replaced by | Example |
|---|---|---|
| %a | Abbreviated weekday name * | Thu |
| %A | Full weekday name * | Thursday |
| %b | Abbreviated month name * | Aug |
| %B | Full month name * | August |
| %c | Date and time representation * | 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 |
| %h | Abbreviated month name * (same as %b) | Aug |
| %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 * | 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 * | 08/23/01 |
| %X | Time representation * | 14:55:02 |
| %y | Year, last two digits (00-99) | 01 |
| %Y | Year | 2001 |
| %z | ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100),If timezone cannot be determined, no characters | +100 |
| %Z | Timezone name or abbreviation *,if timezone cannot be determined, no characters | CDT |
| %% | A % sign | % |
