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 Convert year to 1, 2 and 4 char year  
  
 Usage: sh_year -year <year> 
  
        <year>  is the year you want converted to 1, 2, 4 char.
  
 Assumptions: Given input year which is < 60  --> yr4 = 2000 + year 
              Given input year which is >= 60 --> yr4 = 1900 + year 
  
 Examples: sh_year -year   01 
           sh_year -year 1999 
  
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