My flight left Swampy on 17/1/14, near 10 pm, and arrived at Clark around 1 am on 18/1/14, a day later. I wondered what date they were going to stamp me in on, as I was arriving in the wee hours of the 18th (without a visa).
I got stamped in on 18/1, and given to 17/2. Seems to me like that's 31 days, inclusive...?
BTW, I had bought a one-way 'throwaway' ticket from Clark to Hong Kong (1,500 Pesos) that was valid within the initial 30 days of my stay here. This satisfied Tiger at Swampy. No questions, no hassles. I asked about the necessity of buying this ticket out within the initial 30 days, 'cause coming in with or without a visa, you *can* extend your stay. The check-in lady referred me to an airline guy, whose English was really bad, and he seemed a bit nervous, he said something like 'blah, blah, blah, the law.' I think he was somewhat taken aback by my question, hence the bad English, etc., but I also tend to think I would have been in for some hassle if I *hadn't* had my throwaway to HK.
FYI.