Davydova married boxing coach Pavel Filatov on 1 June 1983. They have two sons, Dmitrii (born 21 February 1985) and Anton (28 June 1995. The family moved to Canada in 1991. Davydova now owns Gemini Gymnastics, a high performance gymnastics club in Oshawa, Ontario where she has been a coach since immigrating to Canada, and Head Coach since 1999.  Some of her better known gymnasts include Stephanie Capucitti, Sarah Deegan, Danielle Hicks, Katherine Fairhurst, Kristina Vaculik, Brittnee Habbib, Kelsey Hope. She was beam coach for the Canadian womens team at the 1995 World Championships in Artistic Gymnastics and one of the Canadian womens team coaches at the 2002 Commonwealth Games. Davydova was twice named Gymnastics Canada Gymnastique coach of the year. In October 2005 Elena was chosen for the Coaching Association of Canadas Women in Coaching National Team Coaching Apprenticeship Program. In 2005, 2006 and 2010 Gymnastics Canada Gymnastique awarded Elena and long-time associate coach, Valery Yahchybekov, as the "Junior High Performance Coaches of the Year". Gemini Gymnastics has been recognised by GCG as Club of Excellence for 10 consecutive years since the inception of the awards in 2001. It is 1 of only 2 clubs to do so.  In 2006 Gemini received the prestigious Gymnastics Canada Ed Broughan award for "Club of the Year". As of 2012 Gemini have produced 15 Canadian AA champions,8 Elite Canada AA champions,21 Eastern Canada AA champions,98 Ontario provincial AA champions plus gymnasts who have won a host of other medals and awards. In September 2007 Kristina Vaculik and Rebecca Simbudhas of Gemini represented Canada at the World Championships. In April 2008 Vaculik won gold and silver World Cup trophies. She was the Canadian team reserve at the Beijing Olympics. In March 2010, Vaculik earned 2 gold and 2 silver medals at the Cottbus World Cup, an unprecedented result for Canadian Artistic womens gymnastics. 
Question: How many years after Davydova's second son was born did she become Head Coach at Gemini Gymnastics?
Answer: 4