Short answer. It is a condition, not a period. Article 1193 says a day certain is one that must necessarily come, although it may not be known when. If the uncertainty is whether the day will come at all, the obligation is conditional, not one you can simply count on arriving.
What the law says
A day certain is understood to be that which must necessarily come, although it may not be known when. If the uncertainty consists in whether the day will come or not, the obligation is conditional
Civil Code, Article 1193 — Obligations With a Period; Day Certain. Read the full provision →
The test is certainty, not timing
Article 1193 draws the line by asking whether the event is bound to happen. A day certain, which makes an obligation one with a period, is that which must necessarily come, although it may not be known when. The unknown timing does not matter — a person's death, for example, is a day certain because it will surely come even though no one knows the date. What controls is inevitability. If the event you are depending on will definitely occur sooner or later, you have a period. If it might never occur at all, you do not.
An 'if it happens' event is a condition
The article resolves your situation squarely: if the uncertainty consists in whether the day will come or not, the obligation is conditional. When the whole deal hangs on something that may or may not ever take place — a sale closing, a permit being granted, a third person deciding to act — the future event is a condition, not a period. That reclassification matters, because the article then sends you to the rules on conditional obligations rather than the rules on periods. What looked like a date you could plan around is really a contingency that may leave the obligation with no effect.
Why the difference is not academic
A period only delays an obligation that is otherwise certain to become demandable; when the day arrives, performance is due. A condition, by contrast, decides whether the obligation ever takes effect at all. So if the event you are relying on is treated as a condition and it never happens, the other side may owe you nothing, because the obligation was suspended on something that did not come to pass. Calling an uncertain event a 'period' in your contract does not change its legal nature — the law looks at whether the event must necessarily come, not at the label the parties used.
What to watch for in your deal
Because so much turns on this, be clear-eyed about the event your deal depends on. Ask whether it is truly bound to occur, or whether it merely might. If it might not, treat it as a condition and expect the rules on conditional obligations to govern what happens if it fails. Where you need certainty, the safer course is to tie performance to a genuine day certain, or to spell out what each side must do if the uncertain event does not materialise, rather than assuming an event that may never happen gives you a date you can count on.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Toyo Seat Philippines Corporation/Yoshihiro Takahama vs. Annabelle C. Velasco, et al, G.R. No. 240774, March 3, 2021 — read the decision on LawPhil →
- Maynilad Water Services, Inc. vs. The Secretary of the Department of Environment and Natural, G.R. No. 202897 / G.R. No. 206823 / G.R. No. 207969, August 6, 2019 — read the decision on LawPhil →
- Congregation of the Religious of the Virgin Mary, etc. vs. Emilio Orola, et al, G.R. No. 169790, April 30, 2008 — read the decision on LawPhil →
- Dr. Daniel Vazquez, et al. vs. Ayala Corporation, G.R. No. 149734, November 19, 2004 — read the decision on LawPhil →