Answer

Yes, you can take Upvas Pachkhan at 3 pm, but with an important condition:

• If you have already eaten or drunk something after sunrise, then the Upvas Pachkhan is generally taken from that time onward, according to the vow you are taking.
• If you want to observe a full traditional Upvas, it is usually taken with proper Pachkhan before eating, commonly in the morning.

Explanation

In Jain practice, Pachkhan means taking a conscious vow of restraint. If at 3 pm you decide to stop all food until the next day, you may take the appropriate Pachkhan from that moment, depending on your tradition and guidance from a Guru or knowledgeable elder.

However, whether it counts as a full Upvas in the strict traditional sense may depend on:

• whether you ate earlier,
• what type of Pachkhan you take,
• your sect/tradition,
• and the guidance of your Guru.

Takeaway

You may take Pachkhan at 3 pm for restraint from now onward, but for a proper traditional Upvas, it is best to follow the guidance of your Guru, Upashray, or knowledgeable Jain elder.