From 37c470e8c0df99bd47f7054834e0db93b75ab073 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C4=81rti=C5=86=C5=A1?=
<liepumartins@users.noreply.github.com>
Date: Tue, 19 Jun 2018 15:28:40 +0300
Subject: Ability to parse dates further in future
Golangs time.Duration uses nanoseconds, thus it is limited to approximately 290 years.
---
date.go | 23 ++++++++++++++++++++++-
date_test.go | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 64 insertions(+), 1 deletion(-)
create mode 100644 date_test.go
diff --git a/date.go b/date.go
index a493866..e078374 100644
--- a/date.go
+++ b/date.go
@@ -15,7 +15,20 @@ func timeToUTCTime(t time.Time) time.Time {
// timeToExcelTime provides function to convert time to Excel time.
func timeToExcelTime(t time.Time) float64 {
- return float64(t.UnixNano())/8.64e13 + 25569.0
+ // TODO in future this should probably also handle date1904 and like TimeFromExcelTime
+ var excelTime float64
+ excelTime = 0
+ // check if UnixNano would be out of int64 range
+ for t.Unix() > 9223372036 {
+ // reduce by aprox. 290 years, which is max for int64 nanoseconds
+ deltaDays := 290 * 364
+ delta := time.Duration(deltaDays * 8.64e13)
+ excelTime = excelTime + float64(deltaDays)
+ t = t.Add(-delta)
+ }
+ // finally add remainder of UnixNano to keep nano precision
+ // and 25569 which is days between 1900 and 1970
+ return excelTime + float64(t.UnixNano())/8.64e13 + 25569.0
}
// shiftJulianToNoon provides function to process julian date to noon.
@@ -90,6 +103,7 @@ func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
// timeFromExcelTime provides function to convert an excelTime representation
// (stored as a floating point number) to a time.Time.
func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
+ const MDD int64 = 106750 // Max time.Duration Days, aprox. 290 years
var date time.Time
var intPart = int64(excelTime)
// Excel uses Julian dates prior to March 1st 1900, and Gregorian
@@ -113,6 +127,13 @@ func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
} else {
date = time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)
}
+
+ // Duration is limited to aprox. 290 years
+ for intPart > MDD {
+ durationDays := time.Duration(MDD) * time.Hour * 24
+ date = date.Add(durationDays)
+ intPart = intPart - MDD
+ }
durationDays := time.Duration(intPart) * time.Hour * 24
durationPart := time.Duration(dayNanoSeconds * floatPart)
return date.Add(durationDays).Add(durationPart)
diff --git a/date_test.go b/date_test.go
new file mode 100644
index 0000000..bf071e0
--- /dev/null
+++ b/date_test.go
@@ -0,0 +1,42 @@
+package excelize
+
+import (
+ "testing"
+ "time"
+)
+
+type dateTest struct {
+ ExcelValue float64
+ GoValue time.Time
+}
+
+func TestTimeToExcelTime(t *testing.T) {
+ trueExpectedInputList := []dateTest {
+ {0.0, time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)},
+ {25569.0, time.Unix(0, 0)},
+ {43269.0, time.Date(2018, 6, 18, 0, 0, 0, 0, time.UTC)},
+ {401769.0, time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)},
+ }
+
+ for _, test := range trueExpectedInputList {
+ if test.ExcelValue != timeToExcelTime(test.GoValue) {
+ t.Fatalf("Expected %v from %v = true, got %v\n", test.ExcelValue, test.GoValue, timeToExcelTime(test.GoValue))
+ }
+ }
+}
+
+func TestTimeFromExcelTime(t *testing.T) {
+ trueExpectedInputList := []dateTest {
+ {0.0, time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)},
+ {60.0, time.Date(1900, 2, 28, 0, 0, 0, 0, time.UTC)},
+ {61.0, time.Date(1900, 3, 1, 0, 0, 0, 0, time.UTC)},
+ {41275.0, time.Date(2013, 1, 1, 0, 0, 0, 0, time.UTC)},
+ {401769.0, time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)},
+ }
+
+ for _, test := range trueExpectedInputList {
+ if test.GoValue != timeFromExcelTime(test.ExcelValue, false) {
+ t.Fatalf("Expected %v from %v = true, got %v\n", test.GoValue, test.ExcelValue, timeFromExcelTime(test.ExcelValue, false))
+ }
+ }
+}
--
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