QBIC, 48 bytes
?@It's `+right$(_D,4)+@ already, folks, go home.
I really should start working on substring...
@ ... ` String literal:
- creates a string with all the text from @ to `,
- stores it as the first available string var (A$)
- and injects A$ at the current point in the QBasic translated code.
+ String concatenation
right$ QBasic function to take characters from the right.
_D QBIC's call to get the system date as dd-mm-yyyy (_d gets the time)
+@ ... Second string lit (B$). Doesn't need the closing ` because of EOF.
Update: Substring saves me 4 bytes:
?@It's `+_s_D,-4|+@ already, folks, go home.