Fixed vs Evergreen vs Dynamic: Which Timer Do You Need?
CountdownMail offers three types of countdown timers, and each one solves a different problem. Picking the wrong type means extra work later or, worse, timers that confuse your subscribers. This guide breaks down the differences so you can choose correctly the first time.
Quick Comparison
Before diving into details, here is a side-by-side overview:
| Feature | Fixed Date | Evergreen | Dynamic |
|---|---|---|---|
| Deadline | Same for everyone | Unique per recipient | Unique per recipient |
| Who sets the time? | You, when creating | Moment of open or send | Your system (CRM, backend) |
| Setup complexity | Simple | Medium | Requires integration |
| Typical use case | Sales, events, holidays | Funnels, automations | CRM personalization |
Now let's look at each type in detail.
Fixed Date Timer: The Classic Choice
When everyone needs to see the same deadline
How It Works
You set a specific end date and time. Every recipient sees the same countdown to that exact moment, regardless of when they open the email or where they are located.
User A and User B see the same time remaining regardless of when they open.
Best Use Cases
Holiday Sales
Black Friday, New Year, Valentine's Day promotions
Webinars & Events
Conferences, live streams, product launches
Limited Promotions
"This weekend only" or seasonal offers
Setup Steps
- In "Countdown Timer Type" select Fixed Date
- Set the end date and time
- Choose the appropriate time zone
- Copy the embed code and paste it into your email
This is the simplest timer type. No special code or integrations required.
Evergreen Timer: Personal Urgency
When each recipient needs their own countdown
How It Works
Each recipient gets their own personal deadline. Instead of picking a specific date, you set a duration, for example 48 hours. The countdown starts individually for each person based on when they open the email or when it was sent to them.
User B's countdown starts later. Both get the full duration.
Two Trigger Options
When email is opened
Timer starts when the recipient opens the email for the first time.
- Server saves the first open time for each unique ID
- Subsequent opens show remaining time
- Works for most email service providers
When email is sent
Timer starts at the moment your ESP sends the email.
- ESP passes a timestamp in the URL
- Nothing is saved on CountdownMail servers
- Use when countdown must begin immediately
Note: Not all email service providers support the "when sent" trigger. If your ESP is not on the list, use the "when opened" option instead.
Best Use Cases
Abandoned Carts
"Complete your order within 24 hours"
Trial Expiration
"Your free trial ends in 3 days"
Welcome Series
"20% off for new subscribers, 48 hours only"
Setup Steps
- In "Countdown Timer Type" select Evergreen
- Set the duration (days, hours, minutes)
- In Embed Options, select your email service provider
- Choose the trigger: "when opened" or "when sent"
- Copy the generated code and paste it into your email template
The generated embedded code will contain the appropriate parameters based on your trigger choice:
When opened
/xyz.gif?id={unique_recipient_id} When sent
/xyz.gif?send_time={timestamp} Important: The code must contain a unique ID for each recipient. If you select the wrong ESP, the merge tag will not be replaced, and the timer will not work correctly. Double-check your selection before sending.
For detailed instructions, see our Evergreen Timer Setup Guide.
Dynamic Timer: Ultimate Control
When you need different deadlines for different people
How It Works
The deadline is passed directly in the image URL with each request. Your system (CRM, backend, or e-commerce platform) determines what deadline to show each recipient. This gives you complete control but requires technical integration.
Example: VIP Personalized Offers
Your backend generates a unique URL for each customer
For John (VIP customer):
...i.countdownmail.com/xyz.gif?end_date_time=2025-12-20T23:59:59+00:00 John sees: until December 20 (UTC)
For Jane (new customer):
...i.countdownmail.com/xyz.gif?end_date_time=2025-12-15T23:59:59-07:00 Jane sees: until December 15 (New York)
Different deadlines for different customers based on your business rules.
Technical Parameters
The main parameter is end_date_time. ISO 8601 works best, but the timer is flexible and accepts many date and time formats as well.
Format
YYYY-MM-DDTHH:MM:SS+HH:MM Examples
?end_date_time=2025-12-31T23:59:59+00:00 (UTC)?end_date_time=2025-12-31T23:59:59-05:00 (New York)?end_date_time=2025-12-31T23:59:59+01:00 (Paris)Best Use Cases
Personalized Coupons from CRM
Each customer has their own discount expiration based on their profile
Shipping Deadlines
"Order by X to receive by Y" with calculated dates
Complex Business Rules
Deadline depends on plan tier, purchase history, or segment
E-commerce Integrations
Shopify, WooCommerce, or custom platforms passing deadlines
Setup Steps
- In "Countdown Timer Type" select Dynamic
- Customize the timer appearance
- Copy the base URL
- In your system, add the
end_date_timeparameter for each recipient
<!-- Your backend generates code like this: -->
<img src="https://i.countdownmail.com/xyz.gif?end_date_time=2025-12-20T18:00:00+00:00" alt="countdownmail.com"/>
Note: Dynamic timers require your system to generate URLs with the necessary parameters. This option is best suited for teams with technical resources or ready-made integrations.
Recurring Timer: Reset and Repeat
When you run repeating events with the same schedule
How It Works
This is not a separate timer type but rather a setting in the "After Count" options. After the timer expires, it automatically restarts and begins counting down again. This works with both Fixed Date and Evergreen timers.
With Fixed Date
Setting: Every Friday 6:00 PM + Reset and Repeat
With Evergreen
Setting: 72 hours + Reset and Repeat
Best Use Cases
- Weekly promotions: "Happy hour every Friday" using Fixed Date with Reset
- Regular flash sales: "Flash sale every Monday" with automatic restart
- Always-on urgency: Timer never shows zeros to any recipient
- Recurring personal windows: New 24-hour action window with each cycle using Evergreen with Reset
Setup Steps
- Create a timer (Fixed Date or Evergreen)
- In the Design section, find the "After Count" field
- Select "Reset and Repeat"
- Save the timer
Use with caution: If recipients realize the timer constantly restarts, it may damage their trust. An "eternal sale" can look like manipulation. Use this feature only when it makes sense for your business model.
Which Timer Should You Choose?
Use this decision tree to find the right timer type for your campaign:
Real-World Examples
| Your Campaign | Timer Type | Why This Works |
|---|---|---|
| Black Friday sale | Fixed Date | One deadline for everyone |
| Abandoned cart recovery | Evergreen | Each person gets 24 hours from opening |
| Personalized coupon from Salesforce | Dynamic | CRM determines expiration for each customer |
| "Discount every Monday" | Fixed Date + Reset | Timer restarts weekly |
| Welcome series for new subscribers | Evergreen | 48 hours from receiving the email |
| Webinar on December 15 at 7 PM | Fixed Date | Specific event time |
| Individual shipping deadline | Dynamic | Backend calculates date for each order |
Frequently Asked Questions
Can I change the timer type after creation?
Partially. You can switch any type to Fixed Date because Fixed Date does not require a special embed code. The code from any timer will work.
However, you cannot switch Fixed Date to Evergreen or Fixed Date to Dynamic without changing the embed code. These types require special parameters (?id= or ?end_date_time=) that are not present in Fixed Date timer code. The same limitation applies when switching between Evergreen and Dynamic since they have different URL parameters.
Evergreen or Dynamic? How do I decide for personalized deadlines?
The key difference is where the deadline logic lives:
- Choose Evergreen if the deadline is determined by the moment of open or send. For example, "48 hours from receiving this email." The logic is simple and handled by CountdownMail.
- Choose Dynamic if the deadline is determined by your business logic. For example, "7 days for VIP customers, 3 days for regular customers." Your system must generate the deadline and pass it in the URL.
Does Reset and Repeat work with Evergreen timers?
Yes. Reset and Repeat is a setting in the "After Count" options, and it works with both Fixed Date and Evergreen timers. After expiration, the timer automatically restarts for the next cycle.
What happens if I do not choose a type?
Fixed Date timer is created by default. If you need Evergreen or Dynamic, you must explicitly select it when creating the timer.
What about Apple Mail on iOS 15+?
Apple Mail caches images, which means timers may show incorrect time on reopening. This affects all timer types equally. CountdownMail offers a "Hide Timer in Apple Mail on iOS 15+" option to replace the timer with a transparent pixel for these recipients. Learn more in our Apple Mail troubleshooting guide.
Summary
| Type | Best For | Key Feature |
|---|---|---|
| Fixed Date | Events, sales with a single deadline | Easy to set up, one deadline for all |
| Evergreen | Funnels, automations, sequences | Personal countdown from open or send |
| Dynamic | CRM and backend integrations | Full control, deadline passed in URL |
| Reset and Repeat | Recurring promotions | Setting for Fixed/Evergreen, auto restarts |