Saturday morning: I set a flat of plants out in full sun for 30 minutes in the morning. Don’t forget and leave them out longer then 30 minutes. Set a timer – its too late to start over from seed if you blow it now.
Later in mid afternoon do it again for 30 minutes and bring the plants back in under fluorescent lights.
Sunday: Take the plants out in the morning for 1 hour. Do the same in the mid afternoon.
Monday: Give the plants a rest from full sun. Monday evening look for early signs of sun damage. Damaged plants will start showing whitish patches on the leaves. It looks like a burn. If you see this then halt further hardening off for the rest of the week and start over next Saturday. If the damage is more than minor than also back off on initial exposure times and reduce the daily increments in exposure.
Tuesday (assuming no significant damage on Monday): Put them out for three hours straight.
Wednesday: Four hours.
Thursday: Five Hours.
Friday: Six Hours.
Saturday: Seven Hours.
Sunday: They are hardened off. Leave them out all day from here on.
Note: The above is a guideline that must be modified by your local conditions. If the weather is cloudy and overcast then the times should be lengthened. If the weather suddenly changes from cold & cloudy to warm and sunny then be conservative on the length of sun exposure. Use your good judgment. If you are in doubt then back off a couple days to allow monitoring of any latent damage symptoms. If the plants are rare and not replaceable then be conservative. If you are growing ordinary jalapenos and know you can get replacements at the local nursery then be more gregarious.
One final note: One never really knows how fast you can do something until you have done it too fast. If you are like me and are always pushing the limits then get ready to accept defeat when you go too fast – but make sure that it happens to your ordinary plants and not the special ones.