When I export/copy it, the other half of the last date is cut off.. Thanks
Can we get your code and data in a usable format? It is close to impossible to do any troubleshooting from a screenshot.
Please read the guide you have been given and try to post a proper reproducible example. Be aware that posting a bulk of code and a screenshot can be considered rude around here.
As @ andresec says.
A screenshot is pretty well useless here. we need the actual data.
A very simple and very effective way to supply some data is to use the dput() command.
and then simply copy the output and paste it here. If you have a very large data set then a sample should be fine. To supply us with 100 rows of your data set do
dput(head(Allsites , 100))
Also please see this discussion, which should answer your question: