The standard unit of time in the SI system is the second, historically defined as 1/86400th of a mean solar day. The modern definitions since 1967 is based upon a caesium atom transition. The Earth's rotation is gradually slowing down meaning that in thousands of years' time the second may need to be redefined to bring it back in line with the mean solar day.
The post explains that a year is defined by Earth's orbital motion around the Sun, encompassing three types: the sidereal year (365.256 days), the tropical year (approximately 365.242 days), and the anomalistic year (365.259 days). It discusses their lengths, differences, and the implications for calendars, notably the transition from the Julian to the Gregorian calendar to align with seasonal changes.
Happy New Year to my readers and followers and I hope you have successful 2023. Although for most us the Christmas and New year festivities are over, for followers of the Orthodox form of Christianity, Christmas is yet to come, as they don't celebrate their Christmas until January 7. The reasons for celebrating Christmas 13… Continue reading Christmas Day January 7th?
In 2019 , for the majority of people 21 April was Easter Sunday, one of the most important dates in the Christian calendar. Although Easter is a is a festival celebrating the resurrection of Jesus Christ from the dead, it is also widely marked by non-Christians in the UK, particularly as there are two very welcome public holidays on… Continue reading Easter – 21 April 2019
Merry Christmas to all my readers and followers and I wish you all a happy New Year. The majority of people who celebrate Christmas Day, whether for religious or cultural reasons or both, do so on 25 December.  However, followers of the Orthodox churches generally celebrate Christmas Day thirteen days later, on January 7. The reasons… Continue reading Christmas Day – December 25th or January 7th?
Explaining Science 