Assalaamu alaykum. I recently came to know that Muslims are not allowed to wear/use products with the Nike logo because she was an ancient greek Goddess. I have stopped using such products, but I am confused because we do use the names of the days, like Sunday, Saturday, Monday, etc. These days were named after the Roman gods! January was named after Roman god Janus or Juno. Is using those names haram as well?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

The matter is as you mentioned, that some scholars forbade wearing clothing that has some of the slogans of disbelief, which may be a symbol of their religion or a name of their alleged gods, such as the sign (Nike), which symbolizes the goddess of victory in Greek mythology. Please, refer to fatwa 5810.

As regards the mere use of such words, then this is another matter, as is known. There is publicity in clothes and showing pride, and it may involve a kind of approval. As regards the mere use of words, it is to indicate whatever they designate, regardless of approval or denial. Indeed, the Quran stated some names of false gods; Allah says (what means): {So have you considered Al-Lat and Al-'Uzza? And Manaat, the third - the other one?.} [Quran 53:19-20]

It is known that the mere mention of these names is not an approval of them.

Also, the Prophet described the Dajjaal thus: “I liken him to ‘Abdul-'Uzza (which means slave of Al-'Uzza) ibn Qatan.” [Muslim]

It cannot be said that the Prophet approved of anyone worshiping a false god - Al-'Uzza - because this is no more than relating the name.

To conclude, the mere use of the names of months and days – even though their origin is derived from the names of pagan gods – is not forbidden as long as this is a mere narration of them and because they are proper names of particular months or days, regardless of their origin.

It is known that there is almost no one who uses such names as names of gods or otherwise, but they have become proper names of these months [or days].

Allah knows best.