Dim t As Long = DateTime.DateParse("02/24/2015")
Dim sat As Long = FirstDayOfMonth(7, DateTime.GetMonth(t), DateTime.GetYear(t)) '7 for saturday
Log(DateTime.Date(sat))
Sub FirstDayOfMonth(Day As Int, Month As Int, Year As Int) As Long
Dim s As Long = DateUtils.SetDate(Year, Month, 1)
Dim d As Int = DateTime.GetDayOfWeek(s)
Dim p As Period
p.Initialize
p.Days = (Day + 7 - d) Mod 7
Return DateUtils.AddPeriod(s, p)
End Sub
I only tested it with the values in your question. Make sure to test it more.