There are 365 days in a standard year. This is the most common length of a year in the Gregorian calendar, the most widely used calendar system today.
However, there's a slight irregularity to consider:

Leap year: Every four years, we have a leap year with one additional day. This extra day is added in February, which usually has 28 days. In a leap year, February has 29 days.
So, while a standard year has 365 days, a leap year has 366 days. This leap year system accounts for the Earth's revolution around the sun taking slightly more than 365 days (approximately 365.242 days).