Adding 180 days to April 11, 2011 gives October 8, 2011.
The date 45 days after April 8, 2011 was May 23, 2011.
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Adding 120 days to April 27, 2011 gives August 25, 2011.
Adding 120 days to April 4, 2011 gives August 2, 2011.
Adding 180 days to April 1 2011 gives September 28, 2011.
Subtracting 90 days from April 15, 2011 gives January 15, 2011.
180 days from October 11th, 2011 would be Sunday April 8th, 2012.
The 25th of October 2011.
I will assume you are talking about April 20th 2011. If so, that makes your estimated due date January 11th 2012. This date could be out by a couple of days though. It is also worth noting that babies are rarely born on their due date!
The 18th of September 2009 is 285 days before it. The 11th of April 2011 is 285 days after it.
60 days from January 31, 2011 is April 1, 2011.
I will assume that you are talking about January 1st 2012. If so, your estimated conception date is April 9th 2011. This date could be a couple of days out though. It also depends on your menstrual cycle.