What Really Controls Temporal Reasoning in Large Language Models: Tokenisation or Representation of Time?

Gagan Bhatia, Ahmad Muhammad Isa, Maxime Peyrard, Wei Zhao


Abstract
We present MULTITEMPBENCH, a multilingual temporal reasoning benchmark spanning three tasks, date arithmetic, time zone conversion, and temporal relation extraction across five languages (English, German, Chinese, Arabic, and Hausa) and multiple calendar conventions (Gregorian, Hijri, and Chinese Lunar). MULTITEMPBENCH contains 15,000 examples built by translating 750 curated English questions and expanding each into controlled date-format variants. We evaluate 20 LLMs and introduce the multilingual Date Fragmentation Ratio (mDFR), calibrated with human severity ratings, together with geometric-probing analyses of internal temporal representations. We find tokenisation quality of temporal artefacts is a resource-dependent bottleneck: in low-resource languages and rarer calendar formats, fragmentation disrupts Year/Month/Day separation and accuracy collapses, while high-resource settings are often robust to digit-level splitting. Beyond tokenisation, crossed mixed-effects regression shows that temporal linearity is the strongest predictor of temporal reasoning in high-resource languages, whereas fragmentation is the stronger predictor in low-resource languages.
Anthology ID:
2026.findings-emnlp.2149
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
45931–45949
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URL:
https://aclanthology.org/2026.findings-emnlp.2149/
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Cite (ACL):
Gagan Bhatia, Ahmad Muhammad Isa, Maxime Peyrard, and Wei Zhao. 2026. What Really Controls Temporal Reasoning in Large Language Models: Tokenisation or Representation of Time?. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 45931–45949, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
What Really Controls Temporal Reasoning in Large Language Models: Tokenisation or Representation of Time? (Bhatia et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.2149.pdf