tell application "OmniFocus"
activate
delay 0.2
tell front window
set selectedTrees to selected trees of content
set selectedTasks to every item of selectedTrees
end tell
tell front document
repeat with i from 1 to count of selectedTasks
set theTask to the value of item i of selectedTasks
set currTags to name of tags of theTask
repeat with x from 1 to count of currTags
set currTag to item x of currTags
if currTag = "today" then
set currTag to (first flattened tag whose name is item x of currTags)
remove currTag from tags of theTask
end if
end repeat
mark complete theTask
end repeat
end tell
end tell