Dear Rabbi Simon,
If someone says “It is Lag B’Omer tonight” on the 32nd day of the ‘Omer, has he (inadvertently) counted the ‘Omer or not? May he still recite the berakhah and count the 33rd day of the ‘Omer in the usual way at night?
Thank you for your question.
Although the minhag is to avoid saying “it is Lag B’Omer tonight”, from sunset onward, one who does so may still fulfil the mitzvah, with a berakhah, in the usual way. The reason for this is that the mitzvah is to specify the weeks as well as the days. One who only expresses the day in short (gematria) form, has not fulfilled the mitzvah yet, and therefor may (and should) do so later.
“Make your days count!”
Rabbi Rashi Simon