I'm with Dscanuck, last weekend of Feb to 1st of March.
My first year had the classic January thaw we saw this year...I nearly lost my mind trying to tap fast enough as I thought it would be early and I'd miss it. I didn't, and ended up with some dry holes by the time it started to flow. I tapped on the last weekend in Feb last year and had my barrels full in just a few days. Then it slowed till after March break.
The full moon in March, third full moon of the year, is the Sugar Moon...and last year that was when I had the most sap. I don't have enough experience to definitively say there is a correlation but it worked last year!
Good luck and be patient....the sunami will come.
2014 - 6 buckets, 4 coffee cans and a propane burner - almost 40L of sap and 1.6L of syrup
2015 - 103 taps on gravity. Homemade oil tank arch and a Smoky Lake 2' X 5' hybrid. - 2.66 gallons of syrup
2016 - 101 taps, 550 gallons of sap, ~10 gallons of syrup all dark.
2017 - 138 taps, 225 gallons of sap, 5.55 gallons of dark syrup, still procrastinating on the vac.
2018 - ~150 taps, I lost track of the sap it was incredible!, over 20 gal of syrup, all dark.