Laravel : How to add days to datetime field?
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Laravel: How to Add Days to Datetime Fields using Carbon
When working with date and time manipulation in Laravel applications, developers frequently run into the need to calculate future or past dates based on existing timestamps. A common scenario is needing to set an expiration date (e.g., 30 days after creation) or calculating a future event time from the current moment.
This guide will walk you through the most effective and idiomatic way to add days, months, or years to datetime fields within your Laravel application, leveraging the power of the **Carbon** library.
## Understanding Eloquent Timestamps and Carbon
In Laravel, whenever you use Eloquent models, fields like `created_at` and `updated_at` are automatically cast as Carbon instances. This is a massive advantage, as it means you don't have to manually handle raw string parsing; Eloquent manages the conversion for you.
Consider your example where you want to add 30 days to an existing `updated_at` field in the database:
```php
// Example setup (assuming Article model exists)
$article = Article::find(1);
$originalUpdatedAt = $article->updated_at; // This is a Carbon object
// The goal is to calculate the new date:
$newDate = $originalUpdatedAt->addDays(30);
```
The key to solving your specific problem lies in treating the retrieved timestamp as a Carbon object. When you call methods like `addDays()`, `subMonths()`, or `addYears()` on a Carbon instance, the library handles all the complex timezone and date arithmetic correctly.
## Practical Implementation: Modifying the Timestamp
To modify the record based on this calculation, you need to follow a three-step process: retrieve, calculate, and save.
### Step 1: Retrieve the Record
First, fetch the model you intend to modify from the database.
```php
use App\Models\Article;
use Carbon\Carbon;
// Find the record
$article = Article::find(1);
if ($article) {
// Ensure the timestamp is a valid Carbon object (it usually is via Eloquent)
$originalUpdatedAt = $article->updated_at;
}
```
### Step 2: Perform the Calculation with Carbon
Now, use the powerful methods provided by Carbon to perform the date arithmetic. We create a new instance representing the future date.
```php
// Add 30 days to the existing updated_at time
$futureDate = $originalUpdatedAt->copy()->addDays(30);
```
**Why `->copy()`?** It is an excellent practice to use the `copy()` method when you are manipulating a retrieved object. This ensures that you are modifying a temporary Carbon instance rather than directly mutating the model's property before saving, which can sometimes lead to unexpected side effects if not handled carefully within complex business logic.
### Step 3: Save the New Date Back to the Database
Finally, persist the calculated date back into your database record using Eloquent's `save()` method.
```php
$article->updated_at = $futureDate;
$article->save();
echo "The new updated_at is: " . $article->updated_at->toDateTimeString();
```
## Best Practice: Leveraging Database Functions vs. Application Logic
While manipulating dates in PHP using Carbon (application layer logic) is flexible and highly readable, for very large-scale operations or specific database requirements, sometimes it is more performant to let the database handle the arithmetic directly.
If your goal was purely to calculate an expiration date based on the current time *at the moment of calculation*, you could use raw SQL functions like `DATE_ADD()`:
```php
// Example using Query Builder for bulk operations or specific needs
$newDateTime = DB::raw("DATE_ADD(updated_at, INTERVAL 30 DAY)");
$article->update(['updated_at' => $newDateTime]);
```
However, for standard application-level logic where you are basing the calculation on a retrieved object and need robust timezone awareness, relying on **Carbon** is the superior choice. It provides an excellent abstraction layer over these database functions, making your Laravel code cleaner, more readable, and easier to maintain—a core philosophy behind modern frameworks like **Laravel** itself.
## Conclusion
Adding days to a datetime field in Laravel is best accomplished by utilizing the robust date manipulation features of Carbon. By retrieving the timestamp as a Carbon object, applying methods like `addDays()`, and then saving the result back via Eloquent, you ensure that your application logic is accurate, timezone-aware, and adheres to Laravel's conventions for handling time data. Embrace Carbon; it simplifies complex temporal calculations immensely!