Interestingly, this short story was first published in 1955, so it is set quite soon after the Second World War. This could explain the apparent lack of a father figure during the story and the way that Jerry's mother is so concerned for him and also why Jerry is so concerned for her.

The story as a whole takes place over 11 days during a holiday in France by a beach. You can count the days if you go through the story carefully, which details how many days Jerry took practicing holding his breath and then finally pinpoints the day of the important journey Jerry makes through the tunnel - "On the day before they left, he would do it."

In Doris Lessing's Through the Tunnel, what is the setting's time period?

Through The Tunnel by Doris Lessing which was first published in 1955 and then included in her collection of short stories The Habit of Loving, describes Jerry's symbolic progression from boyhood to perceived manhood. Jerry reveals his maturity, despite being only eleven years old through his "chivalry," towards his seemingly, over-protective mother although she tries to be "neither possessive nor lacking in devotion,"and then, by his confidence and acceptance after he has achieved what he has been working towards doing, no longer finding the need to assert himself by insisting on returning to his beach.  The "real sea" allows Jerry the independence he craves without losing the security he finds with his mother.   

The reader is aware that it is summertime as Jerry, mindful of the fact that he is younger than the other boys he has been watching, contemplates waiting until next summer to try his feat again, knowing that he and his mother return here every summer and have done for several years now. Jerry, who does not tell his mother about his challenge, is finding it difficult, preparing for his journey through the tunnel which he sees as something to strive for, just like the "big boys - men to Jerry." His successful acheivement of his goal is the turning point in his development.