Something that happened at work today has prompted my first ever visit to Pedants' Corner. An irritating new colleague at work reviewed one of my letters and changed 'X is currently away from the office and will return on 20th July' to 'X is currently away from the office and will bereturning on 20th July'.
Is it correct to say 'will be returning' when in fact he will only return once, as a one-off, and won't be doing it for a continuous period?
<runs away in fear of extensive criticism of own post>
Both are correct, he didn't need to change yours. You could claim yours was "better" because it complied with the convention to underline the leaders status by announcing his movements rather than telling people what his plans were.
So if he is annoying make him feel like a bit of a tit by blinding him with dazzling words like "function" and "register".
I think your version is much more sensible as it says exactly what you want to say. To say that X "will be returning on 20th of July" does not actually tell anyone how long it will take X to get back. If I go to Australia and decide to walk back I may well "be returning" on the 20th of July but not actually arrive for months. So the use of the future continuous in this context is pointless, and is less clear than the way you put it originally.
The FC in this context lacks clarity in the sense that it doesn't automatically convey the idea that boss will be at work and ready to talk to people on the 20th. It can be read as suggesting that he will be in transit on the 20th rather than at work. Or only available for the latter part of the day.
It is superfluous and unnecessary to put "will be returning" and annoying.
"will" expresses intent, or that something's might happen if something else doesn't, and is moveable, therefore, if you are definitely going to return, and you have every intention of doing so, and that it's a promise that you are going to, then the correct way of putting the sentence is: "X is currently away from the office and shall return on 20th July"
It annoys me intenssely that so many people have forgotten the word "shall" exists.