- A
Create a calculated field using a formula.
Why wrong: Calculated fields cannot reference previous values.
- B
Create a business rule on 'after' update that sets a 'last_assigned' field when assigned_to changes.
An after business rule can set a field on the same record or related record.
- C
Create a database trigger to log the change.
Why wrong: ServiceNow does not support direct database triggers.
- D
Use a dictionary override to enable auditing.
Why wrong: Auditing logs changes but does not provide a field that can be queried directly.
Question 215 of 500
Tracking Field Change Timestamps in ServiceNow
This SNOW-CAD practice question tests your understanding of core application development. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer needs to capture the time when a field (assigned_to) was last changed. Which approach should be used?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a business rule on 'after' update that sets a 'last_assigned' field when assigned_to changes.
Option B is correct because a business rule running 'after' update can check if the 'assigned_to' field value changed (using previous()) and set a 'last_assigned' field to the current date/time (gs.nowDateTime()). This server-side, platform-native approach reliably captures the timestamp when the field changes. Option A (calculated field) is incorrect because calculated fields are read-only and derive values from other fields; they cannot set a timestamp when a field changes. Option C (database trigger) is not recommended as it bypasses the ServiceNow platform and could cause synchronization issues. Option D (dictionary override to enable auditing) is incorrect because auditing tracks all changes to the field in the audit table but does not store the last change timestamp in a separate field on the record; it would require querying the audit log to find the last change.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a calculated field using a formula.
Why it's wrong here
Calculated fields cannot reference previous values.
- ✓
Create a business rule on 'after' update that sets a 'last_assigned' field when assigned_to changes.
Why this is correct
An after business rule can set a field on the same record or related record.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a database trigger to log the change.
Why it's wrong here
ServiceNow does not support direct database triggers.
- ✗
Use a dictionary override to enable auditing.
Why it's wrong here
Auditing logs changes but does not provide a field that can be queried directly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose calculated fields (Option A) thinking they can dynamically capture timestamps, but calculated fields are read-only and cannot persist a value when a field changes.
Detailed technical explanation
How to think about this question
Under the hood, a business rule on 'after' update runs after the database write completes, allowing you to compare the previous and current values of 'assigned_to' using the 'changes()' API method. If the field changed, you can set the 'last_assigned' field with gs.nowDateTime() to capture the precise server time. A subtle behavior: if the business rule runs on 'before' update, the new value is not yet committed, so 'changes()' may not work reliably; 'after' is the correct choice for this pattern.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the SNOW-CAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this SNOW-CAD question test?
Core Application Development — This question tests Core Application Development — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a business rule on 'after' update that sets a 'last_assigned' field when assigned_to changes. — Option B is correct because a business rule running 'after' update can check if the 'assigned_to' field value changed (using previous()) and set a 'last_assigned' field to the current date/time (gs.nowDateTime()). This server-side, platform-native approach reliably captures the timestamp when the field changes. Option A (calculated field) is incorrect because calculated fields are read-only and derive values from other fields; they cannot set a timestamp when a field changes. Option C (database trigger) is not recommended as it bypasses the ServiceNow platform and could cause synchronization issues. Option D (dictionary override to enable auditing) is incorrect because auditing tracks all changes to the field in the audit table but does not store the last change timestamp in a separate field on the record; it would require querying the audit log to find the last change.
What should I do if I get this SNOW-CAD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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