How to use R apply without changing a function
===

I have a basic character date to posixct function

<code>
charDateToPosixct <-  
  function(chrDate, format, timeZone) {  
     as.POSIXct(chrDate, format=format, tz=timeZone)    
  }
</code>

I have a data frame with date as character and timezone.  
<code>
chrDate <- c("4/25/2012","4/24/2012","4/16/2012","6/30/2012")   
timeZone <- c("US/Eastern","US/Central","US/Pacific","US/Eastern")   
df <- data.frame(date=chrDate,timezone=timeZone)    
str(df)  
'data.frame':   4 obs. of  2 variables:  
 $ date    : Factor w/ 4 levels "4/16/2012","4/24/2012",..: 3 2 1 4  
 $ timezone: Factor w/ 3 levels "US/Central","US/Eastern",..: 2 1 3 2  
</code>

I want to change the data type of date to posixct and so want to apply this function "charDateToPosixct" to each row with the format "%m/%d/%y".


Alternatively I know the workaround by changing the function but i don't want to change the structure of the above function  

This works   
<code>
apply(df,1,charDateToPosixct,"%m/%d/%y")  
</code>
if i change this function to  
<code>
 charDateToPosixct <-   
  function(X,format){  
   as.POSIXct(X[1],format=format,tz=X[2])  
 }   
</code>