"दादा बुधवार को आयेंगे ।"

[ZelieZazou]

The name बुधवार comes from Buddha, right?

[duolingonaut]

Based on the link below, the answer is no.

https://en.wikipedia.org/wiki/Budha

[Ken384225]

What’s the difference between this and, “Grandfather is coming on Wednesday”?

[RanzoG]

Ken ji,

It's just future tense. If you want to translate one way or the other, it's up to you. Duo uses the clear future tense ("will") so as not to confuse with the the present continuous ("is X-ing").