Leap year
The name "leap year" probably comes from the fact that while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, the day of the week in the 12 months following the leap day (from March 1 through February 28 of the following year) will advance two days due to the extra day (thus "leaping over" one of the days in the week). For example, Christmas Day (December 25) fell on a Sunday in 2016, and Monday in 2017, then it fell on Tuesday in 2018, and will fall on Wednesday in 2019 but then "leaps" over Thursday to fall on a Friday in 2020.
July 2
This day is the midpoint of a common year because there are 182 days before and 182 days after it in common years, and 183 before and 182 after in leap years. The exact time of the middle of the year is at noon. In countries that use summer time the actual exact time of the midpoint in a common year is at 1:00 p.m, or 11:00 a.m for countries in the southern hemisphere; this is when 182 days and 12 hours have elapsed and there are 182 days and 12 hours remaining. In a leap year in those countries, the midpoint occurs at 1:00 a.m. on July 2, or 11:00pm on July 1 in the southern hemisphere. This is due to summer time having advanced the time by one hour. It falls on the same day of the week as New Year's Day in common years.