You can use “on” in this sense (platí) but you
have to be more precise about who or what is “on”. S dneškem počítám makes it clear
that the arrangement (domluva) is still ok for
me, whereas “today's on” is impersonal and
therefore vague (s dneškem se
počítá).
So you need to make it clear and say today's still on for me, nebo
I'm still on for today.
Q: Is it ok to say “are we still on for tonight” to a colleague to check
if plans have not been canceled? Is there a more formal way to say it?
A: ‘Are we still on for tonight?’ is a fine colloquial expression, and
can be used in almost any situation. If you wish to be more formal, you could
say, for instance, ‘does our appointment/engagement for this evening still
suit your schedule?’ (Englishforums)
Are we still on for today? This is an expression that you use when you want
to confirm a plan with someone else. So if on Monday you arranged to meet up
with a friend on Thursday, you may want to double-check that you're still on to
meet up!
- Hey Susan, I was just calling to see if we're still on for Wednesday?
- Are we still on to meet up tomorrow? (source)
Cvičení s dětmi (…) Jsme marodi … Dnes nepřijdeme, ve tři máme
besídku … No uvidím jak to stihnu, dneska mám ještě spoustu
zařizování. Když budeme stíhat, tak se na chvilku stavím. Jinak se
uvidíme v pátek… Já s dneškem počítám – I'm still on for
today, today's still on/good/fine/ok for me, I'm
definitely coming/going, I'll definitely be there atd. (source)
S dneškem počítám, jen pro info, může se stát, že … Our
arrangement for (later) today is still on/fine/good/ok for/with me, but just so
you know … I'm still on for (nebo ok for/with) our
arrangement (later) today, but just so you know …