Q: I know that a masjid didn’t look for the moon and I’m following Mecca or a calendar and not the Sunnah, can we still attend their 27th night Qur’an khatam? Wud such an attending bring reward for me and my family? (Sent from area code 702, text)

A: As you have made mention that you know that a given Islamic society is not following the Sunnah of looking for the moon, for you to intentionally support an Islamic society, committee, or any such deviant group warrants the La’na of Allah (the curse of Allah). As you are aware Rasulullah (SAW) made du’a for the one that follows the Sunnah and revives the Sunnah and Allah is also pleased with such a person (derived from Hadith). Likewise, doing to the opposite generates, demands and requests punishment from Allah (SWT)
Allah also says in the Qur’an, “If you love Allah then follow Me (Rasulullah SAW.)” Nowhere does it state follow Mecca or a preplanned calender. Thus, we are to derive from this and other aspects of religion that doing a thing regardless of it being viewed outwardly as religious, if it has a taint of Shaytan’s or a human-made law in it, it will be Baatil.
For example, there are some that have followed the calendar and started Ramadan one day early. Not only is this a mockery of the Qur’an and Sunnah, the Qur’an itself is incomplete for such individuals as it relates to a  Ramadan completion of the Quran as part of it’s Taraweeh.
A complete Ramadaan Qur’an completion can only be considered if it starts and ends at the appropriate start and end times of Ramadan — not a day before and not a day after. Thus, attending a Qur’an completion as presented by you in the question above is not a Qur’an completion — it is a mere mockery to play with the emotions of people by those who administer this fanfare and title it ’27th night’ or as part of a ‘Qur’an completion.’
Such events should better be titled Donation Day Gathering/Muslim meet-up/Ramadan pranks/perceptual unity (rather than actual unity), times have changed so let’s ignore a sunnah night, etc.
We pray that people would unite on aspects of sunnah and limit their toying with the sentiments of people, ameen.
Allah Certainly Knows Best.