@MMRIZE Thanks! Intl.dateTimeFormat worked once I realized what I was trying to compare against was wrong. Probably not actually portable for anyone else but works for me:
let isHoliday = holidays.some(holiday => {
return holiday === new Intl.DateTimeFormat('en-CA').format(current)
})
Overall this isn’t the most efficient code I’ve written. Looping and counting days since a start date for every date cell is expensive. Tim to learn more javascript I guess.