What are the tax implications for a non-resident Indian who has to be in India for more than 3 months?

Pls advise! I am an NRI living in Britain for last 40 plus years. Last year my mother became ill and i have had to come back and forth from india. Since last April 2013 i came to india for one month. Went back to uk, and returned for one more month. This year, i came to india on 17th jan and want to return to uk on 15 May. This would be a total of 181 days. From what i understand i am still classified as an NRI as long as i do not remain in india for more than 182 days. But is this for a continuous period or is it the total number of days within a financial year? Ie do i count my days from April 2013 to march 2014, in which case i can come back later this year, as effectively my quota for 2014 starts on 1st april 2014 and not from date of my arrival. Or have i completely misunderstood and the fact that i've been here sincejan 2013, and if i want to remain in india until may then i will b liable for tax? I would be really grateful for comprehensive advice as i desperately want to spend more time with my mother but my husband is worried about the tax implications!