Well I use the PikaTimer 2.0.2.
In there, put calibrated delay to 480, wanted delay is the delay you got from your seed (seen in the Seed to Time section). Calibrated seconds stays 14 and the wanted second is from your seed again, as well seen in Seed to Time. Hit create timer.
Now, turn your DS back on again, and change the date to the date you chose from Seed to Time. After that, you change the time to the target time. BUT, if the PikaTimer says Minutes Before Target: 1, you have to set it to 15:05 if your target time is 15:06.
Then, make sure you start the timer and save your time on your DS at the same time. Then turn it off, and turn it back on. When the first timer runs out, click your HGSS game in the main window in your DS. Make sure you do it at the same time.