Fix DateTime.days_since_unix_epoch

The implementation of this method is based on the days_from_civil()
function from http://howardhinnant.github.io/date_algorithms.html. Our
implementation incorrectly used the >= operator where it should've used
the > operator, resulting in this method returning the wrong results for
certain dates.

Changelog: fixed

std/src/std/time.inko

@@ -376,7 +376,7 @@ class pub DateTime {
     let month = @month
     let era = if year >= 0 { year } else { year - 399 } / 400
     let yoe = year - (era * 400)
-    let doy = (((153 * if month >= 2 { month - 3 } else { month + 9 }) + 2) / 5)
+    let doy = (((153 * if month > 2 { month - 3 } else { month + 9 }) + 2) / 5)
       + @day - 1
     let doe = (yoe * 365) + (yoe / 4) - (yoe / 100) + doy
 

std/test/std/test_time.inko

@@ -4,6 +4,19 @@ import std.process.(sleep)
 import std.test.Tests
 import std.time.(DateTime, Duration, Instant)
 
+fn ymd(year: Int, month: Int, day: Int) -> DateTime {
+  DateTime {
+    @year = year,
+    @month = month,
+    @day = day,
+    @hour = 12,
+    @minute = 0,
+    @second = 0,
+    @sub_second = 0.0,
+    @utc_offset = 0,
+  }
+}
+
 fn pub tests(t: mut Tests) {
   t.test('Duration.from_secs') fn (t) {
     t.equal(Duration.from_secs(1.2).to_secs, 1.2)
@@ -186,10 +199,12 @@ fn pub tests(t: mut Tests) {
     let t1 = DateTime.from_timestamp(time: 1661538868, utc_offset: 7200)
     let t2 = DateTime.from_timestamp(time: 0, utc_offset: 0)
     let t3 = DateTime.from_timestamp(time: -3600, utc_offset: 0)
+    let t4 = ymd(2024, 2, 3)
 
     t.equal(t1.days_since_unix_epoch, 19_230)
     t.equal(t2.days_since_unix_epoch, 0)
     t.equal(t3.days_since_unix_epoch, -1)
+    t.equal(t4.days_since_unix_epoch, 19_756)
   }
 
   t.test('DateTime.leap_year?') fn (t) {
@@ -232,10 +247,12 @@ fn pub tests(t: mut Tests) {
     let t1 = DateTime.from_timestamp(time: 1661538868, utc_offset: 7200)
     let t2 = DateTime.from_timestamp(time: 0, utc_offset: 0)
     let t3 = DateTime.from_timestamp(time: -3600, utc_offset: 0)
+    let t4 = ymd(2024, 2, 3)
 
     t.equal(t1.to_int, 1661538868)
     t.equal(t2.to_int, 0)
     t.equal(t3.to_int, -3600)
+    t.equal(t4.to_int, 1706961600)
   }
 
   t.test('DateTime.to_float') fn (t) {
@@ -269,6 +286,7 @@ fn pub tests(t: mut Tests) {
     t.equal(t1.cmp(t2), Ordering.Greater)
     t.equal(t2.cmp(t1), Ordering.Less)
     t.equal(t1.cmp(t1), Ordering.Equal)
+    t.equal(ymd(2024, 2, 3).cmp(ymd(2023, 12, 14)), Ordering.Greater)
   }
 
   t.test('DateTime.==') fn (t) {