In some use-case scenarios, you need specific work items to be monitored and executed not in days, but in hours or even minutes. It is usually critical for your process to control them and get specific actions if the time was not met.
Typical examples:
I. You have to set up a governance for SLAs on a specific type of work items, such as customer issues that need to be fixed within less than 4 hours.
II. You need to deliver your newsletter articles by 14:00h on the last day of the month, so the marketing web agency has a few hours left to link them, prepare and run the campaign until the end of the business day.
For any one of the use cases above, you need a notification or some sort of Alarm that indicates to the team where to focus and that they are missing a critical sharp hourly deadline!
How to achieve that via Business Rules?
I. SLA Scenario: We need to make cards burning RED and notify the Manager if a customer sales request takes more than 3 hours in progress!
The Time-based business rule is triggered hourly. So you could do the following:
1. Set up two Custom Fields that will act as a Counter Holder and Flag for the passed hours. 
Notes:
* The Counter Hours is of type Number and in the example we start from 0 up to as many hours as we need, but it could be reversed from 3 and countdown to 0 for example.
* The Counter Flag is of type dropdown with just two options: wait and update.
2. Setup a Business Rule with a Time-Based Rule Trigger where the "Created at" for example was more than 0 days ago (i.e. always true)
The basic conditions should be:
a: The board is the right one
b: The column is "In Progress". Note, if the card is not there, there is no need to count.
c: Add your specific clarifications like Lane is "Customer Requests", Priority is Critical, etc...
Rise the Counter Flag with a value "update".
What will happen is that every single hour, all cards that are in progress and match your conditions will have a custom field Counter Flag set with a value "update".
3. Set up a Series of Business Rules that will increment the passed hours.
a. When the previous business rule is executed it will rise the Counter Flag to Update, so we could chain another business rule to be executed with a trigger Card is Updated.
b. The And conditions should be:
* that Counter Flag is "update",
* The Counter Hours Value is 0.
c. Then set
* Counter Flag to "wait"
* Counter Hours to 1.
What happens is that once the hour has passed the business rule will increment the value in the Counter Hours from 0 to 1.
Now you need to add more business rules for every incrementation 1->2, 2->3, 3->4, and so on for as many as you need to reach the SLA or the Top Hour you need to monitor. Make sure both Custom Fields go in pair, as if you forget to set the Counter Flag to "wait" the next business rule in the sequence will pick it up again and increase the counter. With the Counter Flag with combination of the Counter hours, we make sure only the right incrementation rule is done per hour.
In our example above we need 3 business rules to increment from 0 to 3 hours.
Once this rules are running, this is how a card should look if it's staying for more than 2 hours in your "In Progress" column for example:
4. Final step is to setup a business rule that is again triggered by Card is Updated, but this time if the Counter Hour matches your Top Hour, then apply the final action. 
a: when a card is updated - "Counter Hours" field is changed
b: "Counter Hours" is equal to 3 hours for our example.
c: Update the card to Red color, send notification to the Manager and so on ...
With the last rule, the following had happened:
- the card went in progress
- each hour after that the card Counter Flag was raised for update.
- the 3 incremental rules detect that update is needed and they have been executed in the right sequence to bring the Counter Hours from 0 to 3.
- the last business rule now is triggered with the change of 3 hours passed and the final setup actions are executed.
II. Exact Time Delivery Scenario: You have a sharp delivery time at 14:00 for specific cards. If they are still in progress by that time, make them burning RED and notify the Manager.
Use the Recurring Update Rule and setup several rules that scan all in progress cards at 14:00, 15:00, 16:00 each day.
If they detect a card that contains a tag with mark "14:00" and it's still in Progress and the Deadline is Today, make it RED and notify the Manager.
