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fix timestamp conversion and add-seconds bugs #6

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15eda71
fix timestamp conversion and add-seconds bugs
May 24, 2026
d4ee39b
fix: add leap-year awareness to find-month-from-days
May 25, 2026
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64 changes: 46 additions & 18 deletions test/time.carp
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Original file line number Diff line number Diff line change
Expand Up @@ -186,20 +186,50 @@
"different dates are not equal")

; --- Datetime.to-unix-timestamp / from-unix-timestamp ---
; NOTE: to-unix-timestamp and from-unix-timestamp have pre-existing bugs
; (out-of-bounds array access). Tests are skipped until the library is fixed.
; (assert-equal test
; 0
; (Datetime.to-unix-timestamp &(Datetime.init 1970 1 1
; (Maybe.Just 0) (Maybe.Just 0) (Maybe.Just 0)
; (Maybe.Nothing) (Maybe.Nothing)))
; "unix epoch is timestamp 0")
; (assert-equal test
; &(Datetime.init 1970 1 1
; (Maybe.Just 0) (Maybe.Just 0) (Maybe.Just 0)
; (Maybe.Nothing) (Maybe.Nothing))
; &(Datetime.from-unix-timestamp 0)
; "from-unix-timestamp 0 is epoch")
(assert-equal test
0
(Datetime.to-unix-timestamp
&(Datetime.init 1970
1
1
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Nothing)
(Maybe.Nothing)))
"unix epoch is timestamp 0")
(assert-equal test
&(Datetime.init 1970
1
1
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Nothing)
(Maybe.Nothing))
&(Datetime.from-unix-timestamp 0)
"from-unix-timestamp 0 is epoch")
; Feb 29 leap year round-trip (1972 is a leap year, ts = 68169600)
(assert-equal test
&(Datetime.init 1972
2
29
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Nothing)
(Maybe.Nothing))
&(Datetime.from-unix-timestamp
(Datetime.to-unix-timestamp
&(Datetime.init 1972
2
29
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Just 0)
(Maybe.Nothing)
(Maybe.Nothing))))
"from-unix-timestamp round-trips Feb 29 in leap year")

; --- Datetime.add-seconds ---
(assert-equal test
Expand Down Expand Up @@ -318,10 +348,8 @@
(Maybe.Nothing))
&(Timedelta.days 1)))
"Timedelta.add 1 day advances the day")
; NOTE: add-seconds has an off-by-one bug with negative values;
; subtracting 5 minutes from 00:00:00 yields 23:54:59 instead of 23:55:00.
(assert-equal test
&@"23:54:59"
&@"23:55:00"
&(Datetime.isotime
&(Timedelta.sub
&(Datetime.init 2024
Expand All @@ -333,7 +361,7 @@
(Maybe.Nothing)
(Maybe.Nothing))
&(Timedelta.minutes 5)))
"Timedelta.sub 5 minutes wraps back (off-by-one bug)")
"Timedelta.sub 5 minutes wraps back")

; --- Datetime.strptime ---
; basic date parsing
Expand Down
55 changes: 34 additions & 21 deletions time.carp
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Original file line number Diff line number Diff line change
Expand Up @@ -236,10 +236,13 @@ in the range of `1` to `365` or `366`, depending on whether it’s a leap year."
(doc leap? "checks whether the `Datetime` `dt` is a leap year.")
(defn leap? [dt] (is-leap @(year dt)))

; floor division (matches Python's //)
(hidden div-)
(defn div- [a n] (to-int (floor (/ (Double.from-int a) (Double.from-int n)))))

; weird mod for our purposes (behaves more or less like in Python)
(hidden mod-)
(defn mod- [a n]
(- a (* n (to-int (floor (/ (Double.from-int a) (Double.from-int n)))))))
(defn mod- [a n] (- a (* n (div- a n))))

(doc add-seconds "adds a number of seconds `n` to a `Datetime`.

Expand All @@ -248,24 +251,24 @@ If `n` is negative, it will be subtracted instead.")
(if (neg? n)
(let-do [nd @d
s (Maybe.from @(seconds d) 0)
a (dec (+ s n))]
a (+ s n)]
(set-seconds! &nd (Maybe.Just (mod- a 60)))
(if (>= a 0)
nd
(let-do [m (/ a 60)
(let-do [m (div- a 60)
dm (Maybe.from @(minutes d) 0)
ma (dec (+ m dm))]
ma (+ m dm)]
(set-minutes! &nd (Maybe.Just (mod- ma 60)))
(if (>= ma 0)
nd
(let-do [h (/ ma 60)
(let-do [h (div- ma 60)
dh (Maybe.from @(hours d) 0)
ha (dec (+ h dh))]
ha (+ h dh)]
(set-hours! &nd (Maybe.Just (mod- ha 24)))
(if (>= ha 0)
nd
(let-do [ord (to-ordinal d)
nnd (from-ordinal (dec (+ ord (/ ha 24))))]
nnd (from-ordinal (+ ord (div- ha 24)))]
(set-day! &nd @(day &nnd))
(set-month! &nd @(month &nnd))
(set-year! &nd @(year &nnd))
Expand Down Expand Up @@ -303,10 +306,12 @@ If `n` is negative, it will be subtracted instead.")
(private to-unix)
(hidden to-unix)
(defn to-unix [y m d hh mm ss delta]
(let [yy (for-year
&(Result.unsafe-from-success (Array.range 1970 y 1))
366
365)]
(let [yy (if (<= y 1970)
0
(for-year
&(Result.unsafe-from-success (Array.range 1970 (Int.dec y) 1))
366
365))]
(+ (* yy DAY)
(+
(* @(Array.unsafe-nth &DAYS-BEFORE-MONTH m) DAY)
Expand All @@ -326,23 +331,31 @@ a UNIX timestamp, i.e. the number of seconds elapsed since the 1st of January,
(Maybe.from @(seconds dt) 0)
@(Timezone.delta &tz))))

(private find-month-from-days)
(hidden find-month-from-days)
(defn find-month-from-days [d leap]
(let-do [m 1]
(for [i 2 13]
(let [adj (if (and leap (>= i 3)) 1 0)]
(when (<= (+ @(Array.unsafe-nth &DAYS-BEFORE-MONTH i) adj) d)
(set! m i))))
m))

(doc from-unix-timestamp "returns the `Datetime` equivalent to the UNIX
timestamp `ts`, i.e. the number of seconds elapsed since the 1st of January,
1970.")
(defn from-unix-timestamp [ts]
(let [y (/ ts YEAR)
ld (Int.dec
ld (if (<= y 0)
0
(for-year
&(Result.unsafe-from-success (Array.range 1970 (+ y 1971) 1))
&(Result.unsafe-from-success (Array.range 1970 (+ y 1969) 1))
1
0))
d (- (- (/ ts DAY) (* y 365)) ld)
get-m-until (fn [n]
(Array.reduce &(fn [acc x] (if (< @x n) @x acc))
0
&DAYS-BEFORE-MONTH))
mdays (get-m-until d)
m (Maybe.unsafe-from (Array.index-of &DAYS-BEFORE-MONTH &mdays))
yr (+ y 1970)
m (find-month-from-days d (is-leap yr))
mdays (days-before-month yr m)
nd (- d mdays)
tmpy (* y (* 365 24))
tmpd (* (+ nd (+ ld mdays)) 24)
Expand All @@ -352,7 +365,7 @@ timestamp `ts`, i.e. the number of seconds elapsed since the 1st of January,
tmh (* hh 60)
mm (- (- (- (/ ts 60) tmh) tmd) tmy)
ss (- (- (- (- ts (* 60 mm)) (* tmh 60)) (* tmd 60)) (* tmy 60))]
(init (+ y 1970)
(init yr
m
(Int.inc nd)
(Maybe.Just hh)
Expand Down
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