Calendar year - wikipedia Calendar year This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( June 2009 ) Generally speaking, a calendar year begins on the New Year 's Day of the given calendar system and ends on the day before the following New Year 's Day, and thus consists of a whole number of days. A year can be measured by also starting on any other named day of the calendar, and end on the day before this named day in the following year. This may be termed as a `` years time '' but not in practice or an accepted means to term a Calendar year. To reconcile the calendar year with the astronomical cycle ( which has a fractional number of days ) certain years contain extra days. The Gregorian year, which is in use in most of the world, begins on January 1 and ends on December 31. It has a length of 365 days in an ordinary year, with 8,760 hours, 525,600 minutes, and 31,536,000 seconds ; but 366 days in a leap year, with 8,784 hours, 527,040 minutes, and 31,622,400 seconds. With 97 leap years every 400 years, the year has an average length of 365.2425 days. Other formula - based calendars can have lengths which are further out of step with the solar cycle : for example, the Julian calendar has an average length of 365.25 days, and the Hebrew calendar has an average length of 365.2468 days. The astronomer 's mean tropical year which is averaged over equinoxes and solstices is currently 365.24219 days, slightly shorter than the average length of the year in most calendars, but the astronomer 's value changes over time, so William Herschel 's suggested correction to the Gregorian calendar may become unnecessary by the year 4000. Quarters The calendar year can be divided into four quarters, often abbreviated as Q1, Q2, Q3, and Q4. First quarter, Q1 : 1 January -- 31 March ( 90 days or 91 days in leap years ) Second quarter, Q2 : 1 April -- 30 June ( 91 days ) Third quarter, Q3 : 1 July -- 30 September ( 92 days ) Fourth quarter, Q4 : 1 October -- 31 December ( 92 days ) When combined with a year, the quarter / year combination may be written, for example, as Q42017 or 4Q2017 or 2017Q4. See also Academic term Calendar reform Common year Fiscal year ISO 8601 ISO week date Leap year Model year Tropical year Seasonal year References Jump up ^ `` calendar year ''. Merriam - Webster. Retrieved 6 August 2014. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Calendar_year&oldid=804625949 '' Categories : Calendars Units of time Hidden categories : Articles needing additional references from June 2009 All articles needing additional references Talk About Wikipedia Català Dansk Deutsch Eesti Ελληνικά Español فارسی Hrvatski Nederlands 日本 語 Norsk Norsk nynorsk Română Slovenčina Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் ไทย Українська Võro Edit links This page was last edited on 10 October 2017, at 05 : 41. About Wikipedia

Question: what are the quarters in a calendar year
Answer: First quarter, Q1: 1 January – 31 March (90 days or 91 days in leap years)
Second quarter, Q2: 1 April – 30 June (91 days)
Third quarter, Q3: 1 July – 30 September (92 days)
Fourth quarter, Q4: 1 October – 31 December (92 days)