Legal analysis: the identification of handwriting formation time can be accurate to days within three months, and the test results will be inaccurate if it takes too long. The order of the two signatures is quite different, and the order can be roughly judged from the difference between paper and ink. Generally speaking, when identifying the preparation time of foreign entrustment documents, the submitting unit should be required to provide comparative samples. If the submitting unit can't provide samples, at present, only a few appraisal institutions can appraise the documents made within three months through various determination methods, and very few appraisal institutions of the public security department can appraise the documents made within six months. Due to various objective factors, the detection rate is not high. In this regard, the judicial and technical personnel of the people's court shall examine the appraisal conditions of the entrusted cases and the qualifications and capabilities of the appraisal institutions. If the signature is suspected for more than six months, the submitting unit is required to provide comparison samples.

Legal basis: Article 63 of the Civil Procedure Law of People's Republic of China (PRC). Evidence includes: (1) statements of the parties; (2) Documentary evidence; (3) Physical evidence; (4) Audio-visual materials; (5) Electronic data; (6) Testimony of witnesses; (7) Appraisal opinions; (8) Records of the inquest. Evidence must be verified before it can be used as a basis for ascertaining facts.