\ Print file date from OSFILE control block
  \ =========================================
  \ Prints date from 01/01/1981 to 31/12/2099
  \ On entry  (zp)=>OSFILE control block
  \ On exit   A,X,Y corrupted
  \
  .PrFileDate
  LDY #15:LDA (zp),Y:AND #31:JSR PrDec :\ Day
  JSR PrSlash
  INY    :LDA (zp),Y:AND #15:JSR PrDec :\ Month
  JSR PrSlash
  LDA (zp),Y:LSR A:LSR A:LSR A:DEY     :\ Year b0-b3
  EOR (zp),Y:AND #&1E:EOR (zp),Y:LSR A :\ Merge with year b4-b6
  PHA:CMP #19:LDA #20:SBC #0:JSR PrDec :\ Calculate century
  PLA:SEC:SBC #19:BCS PrDec:ADC #100   :\ Calculate year
  :
  \ Print decimal number by converting it to BCD
  \ --------------------------------------------
  .PrDec
  TAX:LDA #&99:SED:.PrDecLp
  CLC:ADC #1:DEX:BNE PrDecLp:CLD
  :
  \ Print hex number
  \ ----------------
  .PrHex
  PHA:LSR A:LSR A:LSR A:LSR A
  JSR PrNyb:PLA:AND #15:.PrNyb
  SED:CLC:ADC #&90:ADC #&40
  CLD:JMP OSWRCH
  :
  .PrSlash
  LDA #ASC"/":JMP OSWRCH