diff --git a/julian/julian.go b/julian/julian.go
index 2b16a7e..f5846e8 100644
--- a/julian/julian.go
+++ b/julian/julian.go
@@ -120,3 +120,26 @@ func JDateToTime(d Date) time.Time {
 	d = dateDiff(d, offset)
 	return time.Date(d.year, d.month, d.day, 0, 0, 0, 0, time.UTC)
 }
+
+func TimeToJDate(t time.Time) Date {
+	offset := -2
+	// The date when the offset changes in the gregorian calendar is always
+	// 1st of March, so we can always just check the year, and see if we're
+	// past 1st of March year
+	year := t.Year()
+	if t.Month() < time.March {
+		year--
+	}
+
+	borderYear := 100
+	for year >= borderYear {
+		if borderYear%400 != 0 {
+			offset++
+		}
+		borderYear += 100
+	}
+
+	d := Date{t.Year(), t.Month(), t.Day()}
+	d = dateDiff(d, -offset)
+	return d
+}
diff --git a/julian/julian_test.go b/julian/julian_test.go
index d70a4e2..e60a38e 100644
--- a/julian/julian_test.go
+++ b/julian/julian_test.go
@@ -145,3 +145,82 @@ func TestJDateToTime(t *testing.T) {
 		})
 	}
 }
+
+func TestTimeToJDate(t *testing.T) {
+	gDate := func(year int, month time.Month, day int) time.Time {
+		return time.Date(year, month, day, 0, 0, 0, 0, time.UTC)
+	}
+	var tests = []struct {
+		gd   time.Time
+		want Date
+	}{
+		{gDate(100, time.February, 27), Date{100, time.February, 29}},
+		{gDate(100, time.February, 28), Date{100, time.March, 1}},
+		{gDate(100, time.March, 1), Date{100, time.March, 2}},
+		{gDate(200, time.February, 27), Date{200, time.February, 28}},
+		{gDate(200, time.February, 28), Date{200, time.February, 29}},
+		{gDate(200, time.March, 1), Date{200, time.March, 1}},
+		{gDate(300, time.February, 28), Date{300, time.February, 28}},
+		{gDate(300, time.March, 1), Date{300, time.February, 29}},
+		{gDate(300, time.March, 2), Date{300, time.March, 1}},
+		{gDate(500, time.March, 1), Date{500, time.February, 28}},
+		{gDate(500, time.March, 2), Date{500, time.February, 29}},
+		{gDate(500, time.March, 3), Date{500, time.March, 1}},
+		{gDate(600, time.March, 2), Date{600, time.February, 28}},
+		{gDate(600, time.March, 3), Date{600, time.February, 29}},
+		{gDate(600, time.March, 4), Date{600, time.March, 1}},
+		{gDate(700, time.March, 3), Date{700, time.February, 28}},
+		{gDate(700, time.March, 4), Date{700, time.February, 29}},
+		{gDate(700, time.March, 5), Date{700, time.March, 1}},
+		{gDate(900, time.March, 4), Date{900, time.February, 28}},
+		{gDate(900, time.March, 5), Date{900, time.February, 29}},
+		{gDate(900, time.March, 6), Date{900, time.March, 1}},
+		{gDate(1000, time.March, 5), Date{1000, time.February, 28}},
+		{gDate(1000, time.March, 6), Date{1000, time.February, 29}},
+		{gDate(1000, time.March, 7), Date{1000, time.March, 1}},
+		{gDate(1100, time.March, 6), Date{1100, time.February, 28}},
+		{gDate(1100, time.March, 7), Date{1100, time.February, 29}},
+		{gDate(1100, time.March, 8), Date{1100, time.March, 1}},
+		{gDate(1300, time.March, 7), Date{1300, time.February, 28}},
+		{gDate(1300, time.March, 8), Date{1300, time.February, 29}},
+		{gDate(1300, time.March, 9), Date{1300, time.March, 1}},
+		{gDate(1400, time.March, 8), Date{1400, time.February, 28}},
+		{gDate(1400, time.March, 9), Date{1400, time.February, 29}},
+		{gDate(1400, time.March, 10), Date{1400, time.March, 1}},
+		{gDate(1500, time.March, 9), Date{1500, time.February, 28}},
+		{gDate(1500, time.March, 10), Date{1500, time.February, 29}},
+		{gDate(1500, time.March, 11), Date{1500, time.March, 1}},
+		{gDate(1582, time.October, 14), Date{1582, time.October, 4}},
+		{gDate(1582, time.October, 15), Date{1582, time.October, 5}},
+		{gDate(1582, time.October, 16), Date{1582, time.October, 6}},
+		{gDate(1700, time.February, 28), Date{1700, time.February, 18}},
+		{gDate(1700, time.March, 1), Date{1700, time.February, 19}},
+		{gDate(1700, time.March, 10), Date{1700, time.February, 28}},
+		{gDate(1700, time.March, 11), Date{1700, time.February, 29}},
+		{gDate(1700, time.March, 12), Date{1700, time.March, 1}},
+		{gDate(1800, time.February, 28), Date{1800, time.February, 17}},
+		{gDate(1800, time.March, 1), Date{1800, time.February, 18}},
+		{gDate(1800, time.March, 11), Date{1800, time.February, 28}},
+		{gDate(1800, time.March, 12), Date{1800, time.February, 29}},
+		{gDate(1800, time.March, 13), Date{1800, time.March, 1}},
+		{gDate(1900, time.February, 28), Date{1900, time.February, 16}},
+		{gDate(1900, time.March, 1), Date{1900, time.February, 17}},
+		{gDate(1900, time.March, 12), Date{1900, time.February, 28}},
+		{gDate(1900, time.March, 13), Date{1900, time.February, 29}},
+		{gDate(1900, time.March, 14), Date{1900, time.March, 1}},
+		{gDate(2100, time.February, 28), Date{2100, time.February, 15}},
+		{gDate(2100, time.March, 1), Date{2100, time.February, 16}},
+		{gDate(2100, time.March, 13), Date{2100, time.February, 28}},
+		{gDate(2100, time.March, 14), Date{2100, time.February, 29}},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("%v, %v", tt.gd, tt.want)
+		t.Run(testname, func(t *testing.T) {
+			ans := TimeToJDate(tt.gd)
+			if ans != tt.want {
+				t.Errorf("got %v, want %v", ans, tt.want)
+			}
+		})
+	}
+}