Do all companies consider blogging an activity unrelated to work?
No. Some companies view blogs as a good marketing mechanism and encourage employees to create them. If that’s the case, it’s reasonable to update your blog on the company clock. Check with your manager if you’re unsure of your company’s policies. If blogging at the office is OK, you should still be clear about how much time your boss expects you to spend on it. If your blog is strictly extracurricular, do it in your spare time.
