'In your ShowDialog sub
'params.AddAll(.....,TimePeriodToString(Item.Get("Time")),...)
Sub TimePeriodToString (p As Period) As String
Return $"$1.0{p.Hours}:$2.0{p.Minutes}"$
End Sub
Sub StringToTimePeriod (s As String) As Period
Dim m As Matcher = Regex.Matcher("(\d+):(\d+)", s)
Dim p As Period
If m.Find Then
p.Initialize
p.Hours = m.Group(1)
p.Minutes = m.Group(2)
Else
Log("Invalid time string: " & s)
End If
Return p
End Sub