Yes, you can set an item's date manually in BUSY,please follow below steps:
Step 1: Go to Administration and click on configuration.
Step 2: Choose the Voucher Series Configuration option and select the voucher type of that you want to enable voucher numbering for, such as sale, purchase, etc. Then, select the voucher series and click on Voucher Numbering.
Step 3: Choose the Numbering Type as either Automatic or Manual. Then, set the prefix, suffix, and Starting No. as per your needs and click on OK to save the settings.