{"id":14,"date":"2013-12-13T20:16:26","date_gmt":"2013-12-13T20:16:26","guid":{"rendered":"http:\/\/www.eversholt.org.uk\/blog\/?p=14"},"modified":"2013-12-13T20:16:26","modified_gmt":"2013-12-13T20:16:26","slug":"why-isnt-birthdate-arithmetic-easy-birth-years","status":"publish","type":"post","link":"https:\/\/www.eversholt.org.uk\/blog\/why-isnt-birthdate-arithmetic-easy-birth-years\/","title":{"rendered":"Why isn&#8217;t birthdate arithmetic easy? Birth Years."},"content":{"rendered":"<p><span style=\"line-height: 1.714285714; font-size: 1rem;\">When someone says, &#8220;I&#8217;m 60 years old,&#8221; he means, &#8220;I have had my 60th birthday and have not yet had my 61st birthday.&#8221; Traditionally, someone born at any time from 00:00 (midnight) on june 1 to 23:59:59 (just before the next midnight) on June 1 has a birthday on June 1 every year. At least in the UK, by tradition, Independent of what time of day he was born, he will celebrate his birthday starting at 00:00 on each June 1, and will end his birthday at 23:59:59 on each June 1.\u00a0<\/span><\/p>\n<p>Let&#8217;s set aside the effect of time zones on birthdays for <a href=\" http:\/\/www.eversholt.org.uk\/blog\/?p=15\">another post<\/a>. And let&#8217;s set aside the effect of changes of calendar, like the Julian-to-Gregorian change in 1752 in the UK, for another post too.<\/p>\n<p>If the 60-year-old is speaking on a particular date , say yyyy\/mm\/dd, his 60th birthday could have been celebrated, at the latest, on yyyy\/mm\/dd. (So he&#8217;d be speaking on his 60th birthday). It could have been celebrated at the earliest on the day after (yyyy-1)\/mm\/dd. So his birthdate, the date written on his birth certificate, could have been anything from the day after (yyyy-61)\/mm\/dd up to (yyyy-60)\/mm\/dd.<\/p>\n<p>&#8220;The day after&#8221; is just read off the calendar in the normal way. If (yyyy-1)\/mm\/dd is 1953\/Dec\/31, the day after is 1954\/Jan\/1. &#8220;The day after&#8221; 1953\/Feb\/28 was 1953\/Mar\/1. &#8220;the day after&#8221; 1952\/Feb\/28 was 1952\/Feb\/29, because 1952 was a leap year.<\/p>\n<p>If you use the <a href=\"http:\/\/www.eversholt.org.uk\/birthdate\/\">birthdate calculator<\/a>\u00a0to work out birthdate from someone&#8217;s stated age on a given day, and only fill in the &#8216;years&#8217; field of the age, it&#8217;s understood that \u00a0you mean, they&#8217;ve celebrated that many birthdays, but you&#8217;re not sure when their birthday actually is. The birthdate calculator computes an earliest birthdate and a latest birthdate that could possibly make sense, according to the convention described above.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>When someone says, &#8220;I&#8217;m 60 years old,&#8221; he means, &#8220;I have had my 60th birthday and have not yet had my 61st birthday.&#8221; Traditionally, someone born at any time from 00:00 (midnight) on june 1 to 23:59:59 (just before the next midnight) on June 1 has a birthday on June 1 every year. At least [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[3],"tags":[],"class_list":["post-14","post","type-post","status-publish","format-standard","hentry","category-birthdate"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/14","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/comments?post=14"}],"version-history":[{"count":3,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/14\/revisions"}],"predecessor-version":[{"id":19,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/14\/revisions\/19"}],"wp:attachment":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/media?parent=14"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/categories?post=14"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/tags?post=14"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}