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Welcome to the forums!
Computer: On the dashboard click on the gear and choose settings. Click on the device name and scroll until you see clock face.
Phone: tap settings and look for clock display
Also the manual might help you as well its here:
https://staticcs.fitbit.com/content/assets/help/manuals/manual_blaze_en_US.pdf
Hope to see you around the forums! Join in on the discussions forums!
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Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
It's great to welcome you @flappy and @WendyB thanks for stopping by.
To change your clock face from your Android Fitbit app, you just need to do the following:
- Tap the Blaze icon
- Slide down and tap Clock Display
- Select the clock face you prefer and tap Choose
- Sync
I hope this helps, let me know the outcome. 
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