From the second day of פֶּסַח until שָׁבוּעוֹת we count the 49 days of the עֹמֶר.
Counting is done after nightfall. Before counting a Bracha is said:
One counts both days and weeks, as the Torah says (Vayikra 23:15-16):
"And you shall count ... 7 weeks ... you shall count 50 days."
Source: Kitzur Shulchan Aruch 120:1
Sunday, 23 Nissan 5775, 8th day of the Omer