July 21, it is.
The New York Red Bulls confirmed on Jul. 8, the quarterfinal match for the US Open Cup between RBNY and the Philadelphia Union has been settled. The match will be played on Jul. 21 at 4 pm at Red Bull Arena, before the International Champions Cup match between Paris St. Germain and AC Fiorentina that night. The two matches are NOT a doubleheader and will require two separate tickets to enter, according to the team.
The Red Bulls now have a crowded schedule, as they are scheduled to play away in Orlando on July 18th and then an ICC match with the defending Premier League Champions, Chelsea FC, on the 22nd.
It was originally reported that the game could be moved to July 15th to relieve some of the scheduling difficulties that the Red Bulls were facing— that date however created a conflict for the Union who had a friendly scheduled with recently promoted Premier League team AFC Bournemouth on the 14th.
Twitter has reacted negatively to the early start time for a Tuesday game which was necessitated by the PSG and Fiorentina game already scheduled for 8:30 pm. The Union reportedly offered to host the USOC game which the Red Bulls front office declined.
This would create an issue for the Red Bulls who would need to navigate 3 games in the course of 5 days, on a pitch that at one point will have three games played in just over 24 hours. Players from USL side NYRB II can't be used in the US Open Cup as they are USL contracts not MLS contracts. Asking players to play in two days has happened before, but at a professional level, it's pretty rare. The Red Bulls may be forced to play it's starters in the USOC and playing NYRB II against Chelsea.