The duration of the first employment spell of workers across five different birth cohorts is investigated using pooled data from the 15th and 20th cycles of the Canadian General Social Survey. These retrospective surveys contain information that spans well over the last half of the 20th century. The data are benchmarked against the Labour Force Survey to emphasize the distinct nature of employment spells vis-a-vis job tenures as commonly used in the literature. Overall, this paper contributes to the debate of employment stability by analyzing the differences between job and employment durations and showing that successive cohorts of workers have had increasingly shorter first employment durations. The analysis finds cohort effects which play a significant role in explaining declining employment tenure. The cohort effects can be seen as a proxy for a number of socio-economic factors that affect the hazard of separation from employment. Separate analysis is completed for men and women by birth cohort. This pattern of declining tenure has occurred for both men and women, but the decline has been far more prominent for men. For men, macroeconomic factors affect the hazard more strongly in more recent cohorts, which is consistent with recessionary periods generating decreasing employment stability across cohorts. For women, cohort effects are consistent with the increasing generosity of maternity leave provisions through Unemployment Insurance.