On the web you actually have to be in Live to send challenges in those time controls. It is a separate game type and link.
Your friend also has to be in the Live interface at the same time.
Unable to invite a friend to a blitz game
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On my phone I get different duration formats for sending a game invite to a friend on the friends' list including blitz and bullet. However, on the web version, the game duration options are only in the form of days.
Why is this the case?