今日工作需要记录文件路径和到期时间，用到了CTime类和CtimeSpan类进行时间的格式化和相加减操作。记录下来以备后用。
CTime的诸如GetDays()这些函数见名知义，不用记录。
CTime的Format函数原型为：
CString Format(
LPCTSTR pszFormat
) const;
CString Format(
UINT nFormatID
) const;
两个参数一个是传const char* 一个是传字符串ID。字符串中由formatting codes进行匹配时间，formatting codes可以在strftime下找到。贴在下面
- %a
-
Abbreviated weekday name
- %A
-
Full weekday name
- %b
-
Abbreviated month name
- %B
-
Full month name
- %c
-
Date and time representation appropriate for locale
- %d
-
Day of month as decimal number (01 – 31)
- %H
-
Hour in 24-hour format (00 – 23)
- %I
-
Hour in 12-hour format (01 – 12)
- %j
-
Day of year as decimal number (001 – 366)
- %m
-
Month as decimal number (01 – 12)
- %M
-
Minute as decimal number (00 – 59)
- %p
-
Current locale's A.M./P.M. indicator for 12-hour clock
- %S
-
Second as decimal number (00 – 59)
- %U
-
Week of year as decimal number, with Sunday as first day of week (00 – 53)
- %w
-
Weekday as decimal number (0 – 6; Sunday is 0)
- %W
-
Week of year as decimal number, with Monday as first day of week (00 – 53)
- %x
-
Date representation for current locale
- %X
-
Time representation for current locale
- %y
-
Year without century, as decimal number (00 – 99)
- %Y
-
Year with century, as decimal number
- %z, %Z
-
Either the time-zone name or time zone abbreviation, depending on registry settings; no characters if time zone is unknown
- %%
-
Percent sign
如果想要输出当前时间的年月日小时分钟可以使用如下代码
CTime time = CTime::GetCurrentTime();
CString strTime = time.Format("%Y-%m-%d %H:%M");
AfxMessageBox(strTime);
和printf函数一样，支持使用#做前缀，例如月份前不想使用0进行补位，可以用%#m表示。
下面说日期的加减，CTime重载了+，-操作符，用来将CTime对象和CTimeSpan对象进行加减。用法如下
CTimeSpan timeSpan(35, 0, 0, 0);
time += timeSpan;
表示将time（CTime对象）加上35天0小时，0分，0秒。