calculate-average-pr-merge-time

name	Calculate Average PR Merge Time
description	Compute the average number of days from PR creation to merge for all merged PRs in December 2024, using correct timestamp parsing and filtering.

Calculate Average PR Merge Time

Overview

Calculate the average time-to-merge in days (rounded to 1 decimal place) for PRs that were successfully merged during December 2024.

Step 1: Filter Merged PRs Only

From the PR query results, identify only PRs where:

• mergedAt is NOT null
• state equals "MERGED" (verify this is the actual state value)

Do NOT include closed-but-unmerged or open PRs in this calculation.

Step 2: Parse Timestamps Correctly

For each merged PR, extract:

• createdAt: The PR creation timestamp (ISO-8601 format, e.g., 2024-12-15T10:30:45Z)
• mergedAt: The PR merge timestamp (ISO-8601 format)

Critical: Use the creation date as the start point, not any other date field.

Step 3: Convert to Days

For each PR:

1. Parse both timestamps as datetime objects (handle timezone info — typically UTC)
2. Calculate the difference: mergedAt - createdAt
3. Convert to total days (may be a float with decimal)
4. Example: If a PR was created on 2024-12-01 at 00:00:00 and merged on 2024-12-02 at 12:00:00, that's 1.5 days

Step 4: Compute Average

• Sum all day values from step 3
• Divide by the count of merged PRs
• Round the result to exactly 1 decimal place (e.g., 1.2, 15.8, 0.5)

Step 5: Validation Check

If your average is significantly higher than expected (e.g., 16+ days):

• Verify you're only including merged PRs (check mergedAt != null)
• Confirm you're measuring from createdAt (not some other field)
• Check if any timestamp parsing errors are inflating the values
• Inspect a few sample PRs manually to spot-check the calculation

Example Pseudocode

merged_prs = [pr for pr in prs if pr.mergedAt is not null and pr.state == "MERGED"]
days_list = []
for pr in merged_prs:
  created = parse_datetime(pr.createdAt)
  merged = parse_datetime(pr.mergedAt)
  days = (merged - created).total_seconds() / 86400
  days_list.append(days)
avg = sum(days_list) / len(days_list)
rounded_avg = round(avg, 1)