anchor.diff:      
       match periodCount with
       | 2 ->
  +      // Two periods mean yyyy.mm.dd
         let firstPeriod = Array.IndexOf(str, Period)
         let secondPeriod = Array.IndexOf(str, Period, firstPeriod + 1)
         let y = numToPeriod str 0 firstPeriod
  
positive.code:   /// Attempts to convert the string to a date time. Returns some datetime if
    /// successful
    let tryDateParse (str:byte[]) (strLength:int) =
      // imperatively check to see if the string contains only numbers and
      // periods as this cuts the function time in half compared to the
      // functional equivalent (Seq.forall)
      let mutable canBe = true
      let mutable i = 0
      let mutable periodCount = 0
  
negative.code:       let d = numToPeriod str (secondPeriod + 1) (strLength)
        tryDate y m d 0
      | 3 ->
        // Three periods mean yyyy.mm.dd.hh
        let firstPeriod = Array.IndexOf(str, Period)
        let secondPeriod = Array.IndexOf(str, Period, firstPeriod + 1)
        let thirdPeriod = Array.IndexOf(str, Period, secondPeriod + 1)
  