Thank youI would just make a video announcing your schedule shift. Besides announcing it on twitter or Facebook (which all your subscribers probably wouldn't see) you could post a bulletin in their news feed (just go to the feed section of your channel to find it) but again, that probably wouldn't guarantee that everyone would see it.
Post with your feed. http://yttalk.com/threads/how-to-get-to-your-feed-one-channel-layout.51254/Is there anyway to let your subs know that you won't be uploading on a certain day? because I've decided that I'm going to upload my video on a sunday instead of today