From 8a5812a776a488fbfaba77df6d2e3225e49ae3b3 Mon Sep 17 00:00:00 2001
From: Martin Yeo <40734014+trexfeathers@users.noreply.github.com>
Date: Tue, 8 Sep 2026 11:00:47 +0100
Subject: [PATCH] Propagate changes from SciTools/iris#7271

---
 templates/github/workflows/ci-benchmarks-run.yml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/templates/github/workflows/ci-benchmarks-run.yml b/templates/github/workflows/ci-benchmarks-run.yml
index c422fcd..c6a4611 100644
--- a/templates/github/workflows/ci-benchmarks-run.yml
+++ b/templates/github/workflows/ci-benchmarks-run.yml
@@ -112,8 +112,10 @@ jobs:
         run: |
           first_commit=${FIRST_COMMIT}
           if [ "$first_commit" == "" ]
+          # 26 hours to cope with variability in GHA start times.
           then
-            first_commit=$(git log --after="$(date -d "1 day ago" +"%Y-%m-%d") 23:00:00" --pretty=format:"%h" | tail -n 1)
+            cutoff_utc=$(date -u -d "26 hours ago" +"%Y-%m-%dT%H:%M:%SZ")
+            first_commit=$(git rev-list --since="$cutoff_utc" --reverse HEAD | head -n 1)
           fi
 
           if [ "$first_commit" != "" ]