diff --git a/rfctime/interface.go b/rfctime/interface.go
index 3dc2996..d197158 100644
--- a/rfctime/interface.go
+++ b/rfctime/interface.go
@@ -43,3 +43,45 @@ type RFCTime interface {
 	GoString() string
 	String() string
 }
+
+type RFCDuration interface {
+	Time() time.Time
+	Serialize() string
+
+	UnmarshalJSON(bytes []byte) error
+	MarshalJSON() ([]byte, error)
+
+	MarshalBinary() ([]byte, error)
+	UnmarshalBinary(data []byte) error
+
+	GobEncode() ([]byte, error)
+	GobDecode(data []byte) error
+
+	MarshalText() ([]byte, error)
+	UnmarshalText(data []byte) error
+
+	After(u RFCTime) bool
+	Before(u RFCTime) bool
+	Equal(u RFCTime) bool
+	IsZero() bool
+	Date() (year int, month time.Month, day int)
+	Year() int
+	Month() time.Month
+	Day() int
+	Weekday() time.Weekday
+	ISOWeek() (year, week int)
+	Clock() (hour, min, sec int)
+	Hour() int
+	Minute() int
+	Second() int
+	Nanosecond() int
+	YearDay() int
+	Sub(u RFCTime) time.Duration
+	Unix() int64
+	UnixMilli() int64
+	UnixMicro() int64
+	UnixNano() int64
+	Format(layout string) string
+	GoString() string
+	String() string
+}
diff --git a/rfctime/seconds.go b/rfctime/seconds.go
new file mode 100644
index 0000000..e185e19
--- /dev/null
+++ b/rfctime/seconds.go
@@ -0,0 +1,59 @@
+package rfctime
+
+import (
+	"encoding/json"
+	"gogs.mikescher.com/BlackForestBytes/goext/timeext"
+	"time"
+)
+
+type SecondsF64 time.Duration
+
+func (d SecondsF64) Duration() time.Duration {
+	return time.Duration(d)
+}
+
+func (d SecondsF64) String() string {
+	return d.Duration().String()
+}
+
+func (d SecondsF64) Nanoseconds() int64 {
+	return d.Duration().Nanoseconds()
+}
+
+func (d SecondsF64) Microseconds() int64 {
+	return d.Duration().Microseconds()
+}
+
+func (d SecondsF64) Milliseconds() int64 {
+	return d.Duration().Milliseconds()
+}
+
+func (d SecondsF64) Seconds() float64 {
+	return d.Duration().Seconds()
+}
+
+func (d SecondsF64) Minutes() float64 {
+	return d.Duration().Minutes()
+}
+
+func (d SecondsF64) Hours() float64 {
+	return d.Duration().Hours()
+}
+
+func (d *SecondsF64) UnmarshalJSON(data []byte) error {
+	var secs float64 = 0
+	if err := json.Unmarshal(data, &secs); err != nil {
+		return err
+	}
+	*d = SecondsF64(timeext.FromSeconds(secs))
+	return nil
+}
+
+func (d SecondsF64) MarshalJSON() ([]byte, error) {
+	secs := d.Seconds()
+	return json.Marshal(secs)
+}
+
+func NewSecondsF64(t time.Duration) SecondsF64 {
+	return SecondsF64(t)
+}