How many seconds are in a day?

There are exactly 86,400 seconds in one day: 24 hours × 60 minutes × 60 seconds = 86,400. One week is 604,800 seconds. One year of 365 days is 31,536,000 seconds. One leap year of 366 days is 31,622,400 seconds.

How do I convert days to seconds?

Multiply the number of days by 86,400. For example, 7 days × 86,400 = 604,800 seconds. For 30 days, the result is 2,592,000 seconds. For 365 days, the result is 31,536,000 seconds.

How do I calculate a future Unix timestamp from a number of days?

Multiply the number of days by 86,400 to get the number of seconds to add. Add this to the current Unix timestamp (current seconds since January 1, 1970). For example, to find the Unix timestamp 7 days from now: current_timestamp + (7 × 86,400) = current_timestamp + 604,800.

Days to Seconds (d to s) Converter

1 d = 86,400 s

1 Day equals 86,400 Seconds (1 d = 86,400 s). Convert Days to Seconds with formula, table, and examples.

One day equals exactly 86,400 seconds. To convert days to seconds, multiply by 86,400. This direction of the conversion is needed whenever a calendar-based duration must be expressed in the SI unit of time — for physics calculations, programming systems, database operations, or any computation that requires dimensional consistency with SI units. Multiplying days by 86,400 produces large numbers quickly. Three days is 259,200 seconds. One week is 604,800 seconds. One year is 31,536,000 seconds (365 days) or 31,622,400 seconds (366 days). These large second counts are the native currency of Unix timestamps, physics formulas, and scientific data systems. In physics, every formula involving time uses seconds as the unit. Calculating the distance a satellite travels in 5 days requires converting those 5 days to 432,000 seconds and multiplying by the orbital speed in metres per second. Calculating the energy radiated by a star over 30 days requires 2,592,000 seconds in the formula. The days-to-seconds conversion is an unavoidable first step in any physics calculation that starts with a day-based duration. In programming, creating future timestamps requires adding seconds to the current time. A 7-day token expiry is implemented by adding 604,800 seconds to the current Unix timestamp. A 30-day subscription period ends 2,592,000 seconds after it begins. Developers routinely multiply days by 86,400 when working with time-based access control, session management, and scheduled jobs.

How to Convert Days to Seconds

s = d × 86,400

Multiply the value in Days by 86,400

Take your value in Days
Multiply by 86,400
Read the result in Seconds

Common Days to Seconds Conversions

Days (d)	Seconds (s)	Status
0.5 d	43,200 s
1 d	86,400 s
2 d	172,800 s
3 d	259,200 s
7 d	604,800 s
10 d	864,000 s
14 d	1,209,600 s
30 d	2,592,000 s
60 d	5,184,000 s
90 d	7,776,000 s
180 d	15,552,000 s
365 d	31,536,000 s
366 d	31,622,400 s
730 d	63,072,000 s
3,650 d	315,360,000 s

Good to Know About Days to Seconds Conversion

31,536,000 — the number of seconds in a year (365 × 86,400) — is as well known in physics and engineering as 86,400 is in computing. Nuclear engineers know that 1 curie of radioactivity involves 3.7 × 10¹⁰ disintegrations per second. Climate scientists know that a gigaton of carbon represents a certain number of years of emissions. In both cases, the 31,536,000-second year bridges the human timescale of years and the scientific timescale of seconds.

Days to Seconds: What You Need to Know

The days-to-seconds conversion is fundamental to distributed systems and network protocols. Many authentication tokens, certificates, and API keys have expiry periods specified in days but implemented in seconds. An SSL/TLS certificate valid for 90 days expires 7,776,000 seconds after issuance. A JWT (JSON Web Token) with a 7-day validity period is configured with an 'exp' (expiry) claim set 604,800 seconds in the future. In scientific data management, experimental timelines specified in days must be converted to seconds for alignment with instrument timestamps. A 14-day experiment generates data from second 0 to second 1,209,600. Matching experiment milestones (day 3, day 7, day 14) to instrument log entries requires converting those day markers to second offsets: 259,200, 604,800, and 1,209,600 respectively. In energy and environmental science, energy balances are calculated in joules (watt-seconds), but measurement periods are described in days. The total solar energy received by one square meter of Earth's surface in 30 days (at average insolation of 1,000 W/m²) is 1,000 × 30 × 86,400 = 2,592,000,000 joules, or 2,592 MJ. The 86,400-second day is the link between the physicist's joule and the meteorologist's day. In legal and contractual computing, contract systems calculate deadlines in seconds from a start timestamp. A 30-day payment term from an invoice date is 2,592,000 seconds after the invoice timestamp. Automated reminder systems trigger at specific second offsets before this deadline — for example, 7 days (604,800 seconds) before expiry. Contract management software relies on this multiplication for every deadline calculation.

What is a Day? d

Exactly 86,400 seconds. The fundamental unit of human daily life, based on one full rotation of the Earth, and the building block of calendars worldwide.

Metric SI Imperial US customary calendar planning project timelines medication schedules

Learn more about Day →

What is a Second? s

The SI base unit of time, defined by the radiation frequency of the caesium-133 atom. Used universally in science, engineering, and everyday timekeeping.

Metric SI Imperial US customary scientific measurement sports timing computing and networking

Learn more about Second →

Going the other way? Use our Seconds to Days converter.

Days to Seconds FAQ

There are exactly 86,400 seconds in one day: 24 hours × 60 minutes × 60 seconds = 86,400. One week is 604,800 seconds. One year of 365 days is 31,536,000 seconds. One leap year of 366 days is 31,622,400 seconds.
Multiply the number of days by 86,400. For example, 7 days × 86,400 = 604,800 seconds. For 30 days, the result is 2,592,000 seconds. For 365 days, the result is 31,536,000 seconds.
Multiply the number of days by 86,400 to get the number of seconds to add. Add this to the current Unix timestamp (current seconds since January 1, 1970). For example, to find the Unix timestamp 7 days from now: current_timestamp + (7 × 86,400) = current_timestamp + 604,800.

Non-Frequently Asked Questions About Days to Seconds

Questions nobody should ask - but someone did.

365 days × 86,400 = 31,536,000 seconds — just over 31.5 million seconds. If that year included a leap day, it would be 31,622,400 seconds. A 1-year-old has been alive for approximately 31.5 million heartbeats (at a baby's resting rate of about 100 BPM), 3,153,600,000,000 neural firings (rough estimate), and somewhere between 0 and 3 genuinely useful words. The seconds-to-accomplishments ratio is still being optimised.
15 years × 365.25 days × 86,400 seconds = approximately 473,364,000 seconds — just under half a billion seconds. In those 473 million seconds, a well-loved dog will have wagged its tail approximately 10 billion times, consumed roughly 5,475 meals, and provided an estimated several billion dollars of collective emotional value to its owners. The seconds-per-wag ratio is remarkably efficient.
30 days × 86,400 seconds = 2,592,000 seconds, so you would accumulate 2,592,000 pennies — which is £25,920 or $25,920. A penny a second for 30 days is a surprisingly effective savings strategy, though sourcing and physically handling 2.59 million individual penny coins would present significant logistical challenges. A bank transfer is recommended.