Closing a deal is a process that involves a lot of "behind the scenes" work and coordination with multiple parties. There may also be delays for various reasons - a deal partner may need to sign, the lead may need to verify carry, the portfolio company might want to push back the closing date, bank holidays can delay wiring, etc. Some deals take longer than others to wrap up.
There are a number of reasons that closing dates change, ranging from the lead filling allocation to changes in the portfolio company's schedule. Unfortunately, this means that the closing date included on the deal page is generally an estimate, and may change.
After the closing process is complete, the deal status on your portfolio page will show as "live."