I broke it down to maybe more steps than what are needed, to show the logic involved. That "T" between date and time caused a bit of extra code to be needed.
on open (dropped_files)
repeat with this_file in dropped_files
tell application "System Events"
set extension to name extension of this_file
set file_kind to kind of this_file
set file_type to file type of this_file
end tell
if extension is "txt" or ¬
file_type is "text" or ¬
file_kind is "plain text" then
set foo to paragraph 1 of (read this_file)
if the first word of foo is "time" then
set bar to words 2 through end of foo
exit repeat
end if
end if
end repeat
set yr to item 1 of bar
set mo to item 2 of bar
set text item delimiters to "T"
set dy to text item 1 of item 3 of bar
set da_date to mo & space & dy & space & yr
set tim to text item 2 of item 3 of bar & ":" & item 4 of bar & ":" & item 5 of bar
set DTG to da_date & ", " & text 1 through -2 of tim
date DTG
end open