for the "front" render ( I assume you mean the latest ):

I found this, which should help.

http://stackoverflow.com/a/39501288/1709587

import os
import platform

def creation_date(path_to_file):
    """
    Try to get the date that a file was created, falling back to when it was
    last modified if that isn't possible.
    See http://stackoverflow.com/a/39501288/1709587 for explanation.
    """
    if platform.system() == 'Windows':
        return os.path.getctime(path_to_file)
    else:
        stat = os.stat(path_to_file)
        try:
            return stat.st_birthtime
        except AttributeError:
            # We're probably on Linux. No easy way to get creation dates here,
            # so we'll settle for when its content was last modified.
            return stat.st_mtime

example of usage:

lof = os.listdir( get_rendercache() )
olddate, oldfile= 0, ""
if lof:
    for f in lof:
        f = os.path.join( rendercache, f )
        creation = creation_date( f )
        if creation > olddate:
            olddate = creation
            oldfile = f 
    print( oldfile )

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