刑法上的时效的英文表达为“limitation”，指的是法律规定的对犯罪行为进行追诉或者执行所判处刑罚的有效期限。

时效有追诉时效和行刑时效之分：

追诉时效（limitation of prosecution），是指我国刑法规定的对犯罪分子追究刑事责任有效期限的制度。超过法定追诉期限，司法机关或有告诉权的人不得再对犯罪人进行追诉，已经追诉的，应撤销案件或不起诉，或终止审判。追诉时效完成，是刑罚请求权消灭的重要事由之一。

行刑时效（limitation of execution），是指刑事法律规定的，对被判刑人执行刑罚有效期限的制度。犯罪人被科处刑罚后，只有在行刑时效期内，刑罚执行机关才有权对犯罪人执行所判处的刑罚。行刑时效期内所判处的刑罚未执行，超过行刑时效期，便不能再对犯罪人执行所判处的刑罚。行刑时效完成，是刑罚执行权消灭的一项重要事由。

我国刑法总则只规定了【追诉时效】，对行刑时效未作规定。

刑法追诉时效参考双语法规：

《中华人民共和国刑法》第八十七条：

犯罪经过下列期限不再追诉：

(一)法定最高刑为不满五年有期徒刑的，经过五年；

five years, when the maximum punishment prescribed is fixed-term imprisonment of less than five years;

(二)法定最高刑为五年以上不满十年有期徒刑的，经过十年；

10 years, when the maximum punishment prescribed is fixed-term imprisonment of not less than five years but less than 10 years;

(三)法定最高刑为十年以上有期徒刑的，经过十五年；

15 years, when the maximum punishment prescribed is fixed-term imprisonment of not less than 10 years; and

(四)法定最高刑为无期徒刑、死刑的，经过二十年。如果二十年以后认为必须追诉的，须报请最高人民检察院核准。

20 years, when the maximum punishment prescribed is life imprisonment or death penalty. If after 20 years it is considered necessary to prosecute a crime, the matter shall be submitted to the Supreme People's Procuratorate for examination and approval.

《中华人民共和国刑法》第八十八条：

在人民检察院、公安机关、国家安全机关立案侦查或者在人民法院受理案件以后，逃避侦查或者审判的，不受追诉期限的限制。

被害人在追诉期限内提出控告，人民法院、人民检察院、公安机关应当立案而不予立案的，不受追诉期限的限制。

No limitation on the period for prosecution shall be imposed with respect to a criminal who escapes from investigation or trial after a People's Procuratorate, public security organ or national security organ files the case or a People's Court accepts the case.

No limitation on the period for prosecution shall be imposed with respect to a case which should have been but is not filed by a People's Court, People's Procuratorate or public security organ after the victim brings a charge within the period for prosecution.

《中华人民共和国刑法》第八十九条：

The limitation period for prosecution shall be counted from the date the crime is committed; if the criminal act is of a continual or continuous nature, it shall be counted from the date the criminal act is terminated. If further crime is committed during a limitation period for prosecution, the limitation period for prosecution of the old crime shall be counted from the date the new crime is committed.

追诉期限从犯罪之日起计算；犯罪行为有连续或者继续状态的，从犯罪行为终了之日起计算。在追诉期限以内又犯罪的，前罪追诉的期限从犯后罪之日起计算。

参考双语例句：

Moreover, under the provisions of paragraph 1, universal criminal jurisdiction is applied to the crimes specified under the Code, including genocide, to which no statute of limitations applies (see table 1), while paragraphs 2 to 11 of article 7 set forth additional crimes (see table 1).

此外，根据第7条第1款的规定，普遍刑事管辖权适用于《刑法》具体列出的罪行，包括不适用追诉时效法的种族灭绝罪(见表1)，第7条第2至11款还补充了有关其他罪行的规定(见表1)。

Plan to extend the limitation period from three to five years for offences punishable by less than three years’ imprisonment, and from three to seven years for offences punishable by more than three years’ imprisonment.

计划将可判处三年以下监禁的犯罪追诉时效期限延长至五年，将可判处三年以上监禁的犯罪追诉时效期限延长至七年。

The Committee is also concerned that, as a result of criminalizing acts of torture pursuant to articles 83–85 and 312 of the Criminal Code, the statute of limitations with respect to offences that would amount to torture is limited to five years.

委员会还感到关切的是，按照《刑法》第83至85条和第312条将酷刑行为定为犯罪之后，酷刑罪的追诉时效限定为五年。