Background: Technical Debt (TD) describes suboptimal software development practices with long-term consequences, such as defects and vulnerabilities. Deadlines are a leading cause of the emergence of TD in software systems. While multiple aspects of TD have been studied, the empirical research findings on the impact of deadlines are still inconclusive. Aims: This study investigates the impact of scheduled deadlines on TD. It analyzes how scheduled deadlines affect code quality, commit activities, and issues in issue-tracking systems. Method: We analyzed eight Open Source Software (OSS) projects with regular release schedules using SonarQube. We analyzed 12.3k commits and 371 releases across these eight OSS projects. The study combined quantitative metrics with qualitative analyses to comprehensively understand TD accumulation under scheduled deadlines. Results: Our findings indicated that some projects had a clear increase in TD as deadlines approached (with above 50% of releases having increasing TD accumulation as deadlines approached), while others managed to maintain roughly the same amount of TD. Analysis of commit activities and issue tracking revealed that deadline proximity could lead to increased commit frequency and bug-related issue creation. Conclusions: Our study highlights that, in some cases, impending deadlines have a clear impact on TD. The findings pinpoint the need to mitigate last-minute coding rushes and the risks associated with deadline-driven TD accumulation.