Whether a game is blitz or standard depends on a formula that takes into account both the Start time and the Increment (Inc) value to get a sense of the total time a game might last. Here is the formula:
BLITZ if_and_only_if (Start + Inc*2/3) < 15
The following table shows the slowest blitz and fastest standard time controls, the dividing line if you will between the two types of matches. [Thanks to schwartzeer for the calculations. :) ]
|Slowest Blitz||Fastest Standard|
As you can see, not every game with more minutes to start is Standard and not every game with few minutes to start is Blitz.
See also: match