Understanding Data Temporality Impact on Large Language Models Pre-training

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Hauptverfasser: Pilchen, Hippolyte, Fabre, Romain, Talla, Franck Signe, Perez, Patrick, Grave, Edouard
Format: Preprint
Veröffentlicht: 2026
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author Pilchen, Hippolyte
Fabre, Romain
Talla, Franck Signe
Perez, Patrick
Grave, Edouard
author_facet Pilchen, Hippolyte
Fabre, Romain
Talla, Franck Signe
Perez, Patrick
Grave, Edouard
contents Large language models (LLMs) are typically trained on shuffled corpora, yielding models whose knowledge is frozen at train time and whose temporal grounding remains poorly understood. In this work, we study the impact of pre-training dynamics on the acquisition of time-sensitive factual knowledge, focusing specifically on data ordering. Our main contributions are twofold. First, we introduce a comprehensive benchmark of over 7,000 temporally grounded questions and an evaluation protocol that enables analysis of whether models correctly associate facts with their corresponding time periods. Second, we pretrain 6B-parameter models on temporally ordered Common Crawl snapshots and compare them against standard shuffled pre-training. Our results show that sequentially trained models match shuffled baselines on general language understanding and common knowledge while consistently exhibiting more up-to-date and temporally precise knowledge. Temporally ordered pre-training yields improved factual freshness, while shuffled pre-training peaks on older data, possibly due to increased factual repetition. These findings, along with the release of our code at https://github.com/kyutai-labs/kairos , checkpoints, and datasets at https://huggingface.co/collections/kyutai/kairos provide a foundation for future research on continual learning for LLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2605_22769
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Understanding Data Temporality Impact on Large Language Models Pre-training
Pilchen, Hippolyte
Fabre, Romain
Talla, Franck Signe
Perez, Patrick
Grave, Edouard
Computation and Language
Artificial Intelligence
Large language models (LLMs) are typically trained on shuffled corpora, yielding models whose knowledge is frozen at train time and whose temporal grounding remains poorly understood. In this work, we study the impact of pre-training dynamics on the acquisition of time-sensitive factual knowledge, focusing specifically on data ordering. Our main contributions are twofold. First, we introduce a comprehensive benchmark of over 7,000 temporally grounded questions and an evaluation protocol that enables analysis of whether models correctly associate facts with their corresponding time periods. Second, we pretrain 6B-parameter models on temporally ordered Common Crawl snapshots and compare them against standard shuffled pre-training. Our results show that sequentially trained models match shuffled baselines on general language understanding and common knowledge while consistently exhibiting more up-to-date and temporally precise knowledge. Temporally ordered pre-training yields improved factual freshness, while shuffled pre-training peaks on older data, possibly due to increased factual repetition. These findings, along with the release of our code at https://github.com/kyutai-labs/kairos , checkpoints, and datasets at https://huggingface.co/collections/kyutai/kairos provide a foundation for future research on continual learning for LLMs.
title Understanding Data Temporality Impact on Large Language Models Pre-training
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2605.22769