Suppose, not hypothetically, that you have a program that optionally takes a time in the past to, for example, report on things as of that time instead of as of right now. You would like to allow people to specify this time as just 'HH:MM', with the meaning being that time today (letting people do 'program --at 08:30'). This is convenient for people using your program but irritatingly hard today with the Python standard library.

(In the following code examples, I need a Unix timestamp and we're working in local time, so I wind up calling time.mktime() . We're working in local time because that's what is useful for us .)

As I discovered or noticed a long time ago, the time module is a thin shim over the C library time functions and inherits their behavior. One of these behaviors is that if you ask time.strptime() to parse a time format of '%H:%M', you get back a struct_time object that is in 1900:

>>> import time
>>> time.strptime("08:10", "%H:%M")
time.struct_time(tm_year=1900, tm_mon=1, tm_mday=1, tm_hour=8, tm_min=10, tm_sec=0, tm_wday=0, tm_yday=1, tm_isdst=-1)

There are two solutions I can think of, the straightforward brute force approach that uses only the time module and a more theoretically correct version using datetime , which comes in two variations depending on whether you have Python 3.14 or not.

The brute force solution is to re-parse a version of the time string with the date added. Suppose that you have a series of time formats that people can give you, including '%H:%M', and you try them all until one works, with code like this:

 for fmt in tfmts:
     try:
         r = time.strptime(tstr, fmt)
         # Fix up %H:%M and %H%M
         if r.tm_year == 1900:
             dt = time.strftime("%Y-%m-%d ", time.localtime(time.time()))
             # replace original r with the revised one.
             r = time.strptime(dt + tstr, "%Y-%m-%d "+fmt)
         return time.mktime(r)
     except ValueError:
         continue

I think the correct, elegant way using only the standard library is to use datetime to combine today's date and the parsed time into a correct datetime object, which can then be turned into a struct_time and passed to time.mktime . Before Python 3.14, I believe this is:

         r = time.strptime(tstr, fmt)
         if r.tm_year == 1900:
             tm = datetime.time(hour=r.tm_hour, minute=r.tm_min)
             today = datetime.date.today()
             dt = datetime.datetime.combine(today, tm)
             r = dt.timetuple()
         return time.mktime(r)

There are variant approaches to the basic transformation I'm doing here but I think this is the most correct one.

If you have Python 3.14 or later, you have datetime.time.strptime() and I think you can do the slightly clearer:

[...]
             tm = datetime.time.strptime(tstr, fmt)
             today = datetime.date.today()
             dt = datetime.datetime.combine(today, tm)
             r = dt.timetuple()
[...]

If you can work with datetime.datetime objects, you can skip converting back to a time.struct_time object. In my case, the eventual result I need is a Unix timestamp so I have no choice.

You can wrap this up into a general function:

def strptime_today(tstr, fmt):
   r = time.strptime(tstr, fmt)
   if r.tm_year != 1900:
      return r
   tm = datetime.time(hour=r.tm_hour, minute=r.tm_min, second=r.tm_sec)
   today = datetime.date.today()
   dt = datetime.datetime.combine(today, tm)
   return dt.timetuple()

This version of time.strptime() will return the time today if given a time format with only hours, minutes, and possibly seconds. Well, technically it will do this if given any format without the year, but dealing with all of the possible missing fields is left as an exercise for the energetic, partly because there's no (relatively) reliable signal for missing months and days the way there is for years. For many programs, a year of 1900 is not even close to being valid and is some sort of mistake at best, but January 1st is a perfectly ordinary day of the year to care about.

(Now that I've written this function I may update my code to use it, instead of the brute force time package only version.)