add UnixZero

Signed-off-by: Brandon Gonzalez <[email protected]>

time.go

@@ -29,6 +29,12 @@ import (
 	"go.mongodb.org/mongo-driver/bson/bsontype"
 )
 
+var (
+	// UnixZero sets the zero unix timestamp we want to compare against.
+	// Unix 0 for an EST timezone is not equivalent to a UTC timezone.
+	UnixZero = time.Unix(0, 0).UTC()
+)
+
 func init() {
 	dt := DateTime{}
 	Default.Add("datetime", &dt, IsDateTime)
@@ -128,6 +134,11 @@ func (t DateTime) IsZero() bool {
 	return time.Time(t).IsZero()
 }
 
+// IsUnixZerom returns whether the date time is equivalent to time.Unix(0, 0).UTC().
+func (t DateTime) IsUnixZero() bool {
+	return time.Time(t) == UnixZero
+}
+
 // MarshalText implements the text marshaller interface
 func (t DateTime) MarshalText() ([]byte, error) {
 	return []byte(t.String()), nil

time_test.go

@@ -63,6 +63,17 @@ func TestIsZero(t *testing.T) {
 	assert.False(t, NewDateTime().IsZero())
 }
 
+func TestIsUnixZero(t *testing.T) {
+	dt := NewDateTime()
+	assert.True(t, dt.IsUnixZero())
+	assert.NotEqual(t, dt.IsZero(), dt.IsUnixZero())
+	// Test configuring UnixZero
+	estLocation := time.FixedZone("EST", int((-5 * time.Hour).Seconds()))
+	estUnixZero := time.Unix(0, 0).In(estLocation)
+	UnixZero = estUnixZero
+	assert.True(t, DateTime(estUnixZero).IsUnixZero())
+}
+
 func TestParseDateTime_errorCases(t *testing.T) {
 	_, err := ParseDateTime("yada")
 	assert.Error(t, err)