Yes, you can change your investment choice at any time.
From your computer
Log into your account to view your current holdings and transaction history in the “Investments” section. Then click "Change my portfolio" to select a different target date fund.
From your mobile device
Log into your account through the mobile app to view your investment holdings and transaction history in the “Accounts” section. Scroll down to "My investments" and click on "View portfolio". Then select "Change my portfolio" to select a different target date fund.