How to format date and time string in C++

问题:

Let's say I have time_t and tm structure. I can't use Boost but MFC. How can I make it a string like following?

Mon Apr 23 17:48:14 2012

Is using sprintf the only way?

回答1:

The C library includes strftime specifically for formatting dates/times. The format you're asking for seems to correspond to something like this:

char buffer[256];

strftime(buffer, sizeof(buffer), "%a %b %d %H:%M:%S %Y", &your_tm);

I believe std::put_time uses a similar format string, though it does relieve you of having to explicitly deal with a buffer. If you want to write the output to a stream, it's quite convenient, but to get it into a string it's not a lot of help -- you'd have to do something like:

std::stringstream buffer;

buffer << std::put_time(&your_tm, "%a %b %d %H:%M:%S %Y");

// now the result is in `buffer.str()`.

std::put_time is new with C++11, but C++03 has a time_put facet in a locale that can do the same thing. If memory serves, I did manage to make it work once, but after that decided it wasn't worth the trouble, and I haven't done it since.

回答2:

I'd try std::put_time. See the link here for information on how to use it. It supports full format strings and such.

回答3:

MFC has COleDateTime which has a contructor that takes time_t (or __time64_t) and has a Format method.

回答4:

ctime() produces strings in that format. It takes a pointer to a time_t.
There's also asctime() that takes a pointer to a struct tm and does the same.

回答5:

CTime obj1(time_tObj);

CString s = obj1.Format( "%a %b %d %H:%M:%S %Y" );

回答6:

If you need to worry about formatting on different locales, don't forget to initialize the CRT with the current locale. This affects COleDateTime too.

setlocale(LC_COLLATE,“.OCP”); // sets the sort order

setlocale(LC_MONETARY, “.OCP”); // sets the currency formatting rules

setlocale(LC_NUMERIC, “.OCP”); // sets the formatting of numerals

setlocale(LC_TIME, “.OCP”); // defines the date/time formatting

See my blog post which ties in MSDN articles and other sources. http://gilesey.wordpress.com/2012/12/30/initailizing-mfccrt-for-consumption-of-regional-settings-internationalizationc