Getting and Processing Dates & Times in PHP like a Pro

As a full-stack and PHP developer for over 5 years, working extensively with date and time handling across various web apps and systems, I want to share some pro tips for properly working with datetimes in PHP.

Handling dates and times correctly is surprisingly tricky, but extremely important for many PHP apps dealing with schedules, logs, time-sensitive data, and human interaction. After seeing many developer mistakes and confusion with PHP datetimes, I figured I‘d write up this comprehensive guide from an expert perspective.

We‘ll cover the key PHP functions, use proper concepts and terminology, visualize how datetimes work, look at common errors, efficient practices, and plenty of examples you can apply directly in your own projects. Time to level up your PHP datetime fu!

Datetime Fundamentals

First, a quick primer on what datetimes fundamentally represent in programming and PHP.

Dates refer to calendar days in a Gregorian calendar system, with a month, day, and year. For example February 14, 2023.

Times specify a time of day, in hours, minutes and seconds. For example 5:42:18 PM.

Timezones are crucial context about which part of the world that date or time pertains to. For example, Eastern Standard Time (UTC-5).

Datetime is the combination of a calendar date, specific time of day, and relevant timezone.

Datetimes can specify points in time anywhere from 1 second accuracy to entire centuries or millennia.

Timestamps are a universal, numerical way to represent any datetime as a simple integer. Timestamps count seconds elapsed since the Unix Epoch time of 00:00:00 UTC on 1 January 1970. This datetime is equivalently denoted as a timestamp of 0.

Let‘s visualize datetime and timestamp relationships:

We‘ll be using these terms and concepts throughout this guide. Now let‘s look at how to accomplish datetime tasks in PHP!

Displaying Current Date & Time

To display the current date and/or time as a formatted string, PHP provides 2 simple ways:

1. Use the date() Function

The date() function takes a format string, and defaults to the current datetime:

echo date(‘m/d/Y‘); // 02/15/2023
echo date(‘H:i:s‘); // 11:42:18  
echo date(‘m/d/Y H:i:s‘); // 02/15/2023 11:42:18

The format string uses these specification letters:

Letter	Description	Example
d	Day of month	01 to 31
m	Numeric month	02
Y	Full year	2023
H	24-hour hour	11
i	Minutes	42
s	Seconds	18

See all date() formats here.

While simple, using date() has drawbacks:

• Hardcoded formats
• No timezone support
• Limited functionality

2. Create a DateTime Instance

A more flexible approach is to use the built-in DateTime class which models a datetime:

$now = new DateTime();
echo $now->format(‘m/d/Y H:i:s‘); // 02/15/2023 11:42:18  

We use format() to customize display, instead of hardcoding.

Benefits of the DateTime class:

• Encapsulates datetime logic in an Object
• Many useful methods like format(), getTimezone()
• Supports timezones and offsets
• Easier datetime modifications
• More readable OOP style

In general, favor DateTime over date() unless you specifically need a simple string.

Setting the Timezone

By default PHP‘s date and time functions relate to your server‘s configured timezone. This causes problems displaying or converting times for other regions.

You should always explicitly set the timezone:

date_default_timezone_set(‘America/New_York‘);  

Now datetime outputs or conversions will be correctly applied for this timezone.

See all PHP supported timezones. Use timezone abbreviations like UTC, GMT or major city names in the convention Continent/City.

Without an explicit timezone, you will encounter subtle date errors from daylight saving time (DST), or showing incorrect datetimes to application users in different timezones.

Visualizing Timezone Impact

Let‘s look at how the timezone impacts the actual point in time.

First we‘ll generate the current datetime without setting a timezone, relying on the system default which happens to be UTC.

$dt = new DateTime();
echo $dt->format(‘m/d/Y H:i:s T‘);
// 02/15/2023 16:11:48 UTC  

This represents Feburary 15, 2023 at 4:11:48 PM UTC time.

Now if we set the North America Eastern Time timezone (UTC-5), which is currently 5 hours behind UTC:

$dt = new DateTime();
date_default_timezone_set(‘America/New_York‘);  

echo $dt->format(‘m/d/Y H:i:s T‘);
// 02/15/2023 11:11:48 EST

While the datetimes look different, it represents the exact same point in time – Feburary 15, 2023 at 4:11:48 PM UTC. This is visualized below:

We just changed our perspective from UTC to Eastern Standard Time. This is a common source of timezone bugs!

So remember to always set the appropriate timezone for your application‘s target location and audience.

Get a Unix Timestamp

While formatted datetimes are great for display to users, it can be useful to convert dates to timestamps for programming purposes.

Timestamps count elapsed seconds since 00:00:00 UTC on January 1st, 1970, also known as the Unix Epoch. This allows easy date calculations and efficient storage, by representing any datetime as a single integer.

For example the datetime of May 17, 2022 8:11:43 AM UTC equivalently converts to the timestamp integer 1652766703.

We can convert in both directions in PHP:

// Datetime to timestamp
$timestamp = strtotime(‘May 17, 2022 08:11:43‘); 

// Timestamp back to datetime 
echo date(‘m/d/Y H:i:s‘, $timestamp);
// 05/17/2022 08:11:43

The most common timestamp usage is powering UNIX systems, databases, and programming languages. Many databases can store 64-bit integer timestamps that save space over other date types.

Let‘s look closer at the structure of a typical database timestamp column:

As we can see, the datetime can be recovered back from the numeric timestamp using proper formatting.

This makes timestamps a convenient, optimized datetime storage format. Though beware 2038 problem issues from 32-bit architectures!

Manipulate and Modify DateTimes

A powerful aspect of the DateTime class is easy modification, compared to the static nature of strings from date() functions.

We can directly add and subtract intervals. Let‘s start with the current datetime:

$dt = new DateTime(); // 2023-02-15 15:38:04

Add time with ->add():

$dt->add(new DateInterval(‘P10D‘)); 
// 2023-02-25 15:38:04  

$dt->add(new DateInterval(‘PT2H30M‘));
// 2023-02-25 18:08:04

Subtract time with ->sub():

$dt->sub(new DateInterval(‘P30D‘));
// 2023-01-16 15:38:04

$dt->sub(new DateInterval(‘PT90M‘)); 
// 2023-01-16 13:48:04 

We modify it by creating DateInterval objects which follow ISO 8601 duration standard with easy letter notation:

Letter	Unit to Add/Subtract	Example
P	Period of Years/Months/Days	P10D = 10 Days
T	Time Period of Hours/Minutes/Seconds	PT90M = 90 Minutes

This makes datetime math a breeze!

Of course, we can also set datetimes explicitly:

$y2k = new DateTime(‘January 1, 2000‘); 
$moonLanding = DateTime::createFromFormat(‘n/j/Y‘, ‘7/20/1969‘);

Many applications need relative datetimes, like "90 days from now" so DateTime modification is crucial over just using unix stamps.

Localization of DateFormats

Dealing with locale-specific dates is another common requirement.

Dates are often shown differently across languages and regions. For example American style MM/DD/YYYY vs European style DD/MM/YYYY.

We tackle this by defining the locale explicitly:

setlocale(LC_TIME, ‘fr_FR‘); // French locale
echo strftime(‘%A %d %B‘); // same as ‘l j F‘  

setlocale(LC_TIME, ‘en_US‘); // US English locale 
echo strftime(‘%B %d, %Y‘); // same as ‘F j, Y‘

This uses strftime() date formatting along with the locale, achieving localized dates.

The locale influences:

• Translated month/day names
• Default date formatting
• Special handling of DST periods

Let‘s see visual examples of localization in action:

French Locale

mercredi 15 février

United States English Locale

February 15, 2023

Depending on your app‘s audience, handle this appropriately to localize date formatting.

Validate or Restrict Date Ranges

For data integrity, apps often need to validate or restrict datetimes to expected ranges or values.

For example, dates in the future or more than 1 year ago could be invalid. Or restrict time-of-day outside business hours.

The simplest way is just asserting expected properties:

$datetime = new DateTime(‘2025-04-29 03:55:09‘);  

if ($datetime > new DateTime(‘now‘)) {
  echo ‘Invalid future datetime‘;
}

if ($datetime->format(‘G‘) < 9 || $datetime->format(‘G‘) > 17) {
   echo ‘Outside business hours‘; 
}

This checks manually against constraints but gets verbose with complex logic.

A more robust and eloquent solution is using Carbon – a 3rd party DateTime extension. It provides excellent conditional validation:

$datetime = Carbon::parse(‘2025-04-29 03:55:09‘);

if ($datetime->isFuture()) {
  echo ‘Invalid future datetime‘; 
}

if ($datetime->isWeekend()) {
  echo ‘Only allow weekdays‘;
}

Carbon is highly recommended for non-trivial datetime handling!

DateTime Gotchas & Debugging

While datetimes seem simple conceptually, subtle bugs and validation failures can happen. As a senior dev, I want to share some insights handling tricky timezone cases.

A common issue is not realizing your PHP environment relies on default UTC datetimes without timezone awareness. Then attempting to handle some local region‘s wall-clock time goes wrong.

For example this seemingly valid code to get "tomorrow" catastrophically fails because it implicitly uses UTC datetimes unaware of timezones or DST seasons. It will be off by hours returning a past datetime! 🤯

$tomorrow = new DateTime(‘tomorrow‘); // BUG!

An expert PHP developer will immediately recognize this and instead write:

$tz = new DateTimeZone(‘America/New_York‘);  

$tomorrow = new DateTime(‘tomorrow‘, $tz); 

This properly initializes a timezone-aware datetime in the region needed.

Many PHP datetime issues arise from:

• Missing timezone handling
• Confusion over UTC vs local times
• Daylight savings time changes
• Locale formatting assumptions
• Database datatype mismatches
• 32-bit system timestamp overflows

Careful application design and testing around datetimes is needed! Enable full logging and assertions when possible. Tesing edge cases like DST transition hours will reveal bugs.

I recommend always starting datetime work by clearly identifying:

• What is the target region?
• What are valid date ranges or constraints?
• What format(s) need to be supported?
• How will datetimes be stored and retrieved?

DateTime handling may seem simple at first, but has many nuances as applications scale in complexity. Just remember these best practices discussed to avoid major mistakes!

Alternative Languages

While PHP has very capable datetime support, you may encounter or consider alternatives:

JavaScript – Commonly used for front-end UI and validation logic around dates. Its Date object has a lot of overlap with PHP but geared more towards web browsers.

Python – Python‘s datetime and dateutil modules are very robust including timezone handling, similar to PHP. Favorable for backend application logic.

MySQL – SQL databases like MySQL have multiple specialized date/time data types including DATETIME, TIMESTAMP, DATE and TIME. These efficiently store datetimes and run SQL date functions for server-side app logic.

In practice using PHP + JavaScript + MySQL combination handles most date/time use cases!

Putting Datetime Knowledge into Practice

We‘ve covered a ton of conceptual and practical knowledge around datetimes in PHP – now go forth and apply this learning in your own applications!

Proper usage of timezones, timestamps, DateTime formatting/manipulation, localization and validation will give you confidence and skill in wrangling dates and times like an expert developer.

Datetime handling comes up in nearly every common app feature from schedules and calendars to data processing jobs to API inputs/outputs. Level up your abilities today!