(html (head (title "sph-lib (sph time)") (link (@ (rel "stylesheet") (type "text/css") (href "/css/sph.css"))) (meta (@ (name "viewport") (content "width=device-width,initial-scale=1"))) #f) (body () (div (@ (class top)) (nav (a (@ (href "/")) "start") ", " (a (@ (href "/feed.xml")) "feed")) "") (div (@ (class "middle")) (div (@ (class mtime) (title "last modification time of the current page")) "2023-04-05") (section (h1 "(sph time)") (div (p "time as tai or utc nanoseconds since the unix epoch or gregorian calendar dates.") (p "part of " (a (@ (href "../../sph-lib.html")) "sph-lib")) ((section (@ (class "library-description")) (h1 "library description") (div (p "get, manipulate and convert dates and times in scheme.") (p "uses a proleptic gregorian calendar with negative years and a year 0 equivalent to 1 BCE") (p "iso8601 and the gnu date utility include a year zero as well, to which the output is compatible.") (p "international atomic time is used because it does not use leap seconds. with utc it is") (p "not predictable when future leap seconds will be inserted, which makes it impossible to calculate accurate future times with utc.") (p "the implementation does not depend on other time libraries, only on a function that gives the current utc posixtime.") (p "it might also contain useful examples for calendar and time calculation implementors.") (p "objects") (p (((*ENTITY* "nbsp") (*ENTITY* "nbsp")) "utc: integer: utc seconds  since the unix epoch. utc uses leap seconds to conform to (= number-of-days (/ utc-seconds 86400))")) (p (((*ENTITY* "nbsp") (*ENTITY* "nbsp")) "tai: integer: tai seconds since the unix epoch. as elapsed, no leap seconds")) (p (((*ENTITY* "nbsp") (*ENTITY* "nbsp")) "date: vector: gregorian calendar date, daytime and timezone offset")))) (section (@ (class "library-name")) (h1 "module name") (p "(sph time)")) (section (@ (class "library-exports")) (h1 "exported bindings") (div (div (@ (class "doc-bindings")) (div (@ (id "doc-b-" "date->week-day") (class "doc-b")) (div (span (@ (class "type")) "procedure") ": " (span (@ (class "name")) "date->week-day") " " (span (@ (class "first-sig")) "a ->")) "" (div (@ (class "description")) (("from 0-6, with monday being the first day of the week")))) (div (@ (id "doc-b-" "date-add-day") (class "doc-b")) (div (span (@ (class "type")) "procedure") ": " (span (@ (class 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