> Typically, you are "tax resident" if you spend more than 180 days per year in a country. (Note: that doesn't mean that if you split your time equally between three countries you avoid being tax resident at all. If only avoiding tax was that easy...)
I've been informed by my tax consultant that you are tax-resident in the country where you spent the majority of time in a year. If you split your time between three or more countries this still applies.