This message occurs when launching Q++, if Q++ notices that the current date is 30 days or more since the last time you launched Q++. The message contains the current date and time of your workstation, and asks you to confirm if that date and time are correct.
The reaon for this message is that sometimes after a long power outage, your computer's internal battery is discharged and you must reset your system clock. However, being in the diary business, we all work daily with dates that are 1 or 2 years in the future and, for example, we might be tempted to set the system date to 2005, although we are really still in 2003.
This message is there to protect you from such errors which can have negative consequences as most software installed on your workstation will experience problems if, for example, you run them with a system date of 2005 before turining your clock back to 2003.