As well as being Virginia Woolf's original title for what would become Mrs. Dalloway, The Hours refers to the theory of time put forward by the French philosopher Henri Bergson. In his classic work Time and Free Will, Bergson distinguished between clock time, the time by which most of us arrange and organize our lives, and psychological time, in which we experience our inner states. According to Bergson, this is the time by which people truly live their lives as humans.

It is through the latter definition of time that Cunningham is able to explore the inner lives of his characters, all of whom, to some extent, experience a conflict between their inner and outer selves, a conflict which is expressed, respectively, through psychological time and clock time. Psychological time is the medium through which significant memories are recalled and brought to mind, such as when Clarissa reflects on the days she spent with Richard when she was younger.

Psychological time also provides an escape from an often harsh and unforgiving everyday world, a world whose grinding, insistent rhythms are determined by the ticking of the clock. By reading Mrs. Dalloway—the writing of which provided Virginia Woolf with an escape from such a world—Laura is able to deepen and extend her experience way beyond those brief, unfulfilling moments of clock time which she encounters in her daily life.

There is a sense in which the title focuses our attention on time and human mortality, as it makes us think of the "hours" that make up our own lives and how we fill them. This is a key theme in the novel, as the structure of the novel presents us with three characters and how they are obsessed with their own mortality and the hours that they have in life. Time is something that many characters talk about, but perhaps one of the most significant quotes comes at the end of the novel from Clarissa:

Yes, Clarissa thinks, it’s time for the day to be over. We throw our parties; we abandon our families to live alone in Canada; we struggle to write books that do not change the world, despite our gifts and our unstinting efforts, our most extravagant hopes. We live our lives, do whatever we do, and then we sleep—it’s as simple and ordinary as that.

Note how this quote effectively summarises the lives of all the characters and the various struggles and conflicts that make up their lives. How we fill our hours is ultimately insignificant, because against the backdrop of how everybody else fills their time, even actions as radical and as dramatic as "abandoning our families to live alone in Canada" feel rather small and unimportant, because so many people experience similar actions every day. Cunningham seems to use Clarissa as something of a mouthpiece in this quote summarising the main message of this novel: in spite of our apparent differences, all of us are desperately doing what we must do to fill our hours before we die and we can sleep forever.