The Adhkar of the evening can be said from afternoon until sunset and (Part No. 24; Page No. 179) at the beginning of the night. As for the time of Adhkar of the morning, it starts from the break of the dawn until midday. Allah (Glorified and Exalted be He) says,
...and glorify the praises of your Lord before the rising of the sun, and before its setting
Allah (Glorified and Exalted be He) also says,
And remember your Lord within yourself, humbly and with fear and without loudness in words in the mornings, and in the afternoons
The word "afternoons" is the plural of "afternoon", and it is the period before sunset.Allah (Glorified be He) also said,
So glorify Allâh [above all that (evil) they associate with Him (O believers)] when you come up to the evening [i.e. offer the (Maghrib ) sunset and (‘Ishâ’) night prayers], and when you enter the morning [i.e. offer the (Fajr) morning prayer].
And His are all the praises and thanks in the heavens and the earth; and (glorify Him) in the afternoon (i.e. offer ‘Asr prayer) and when you come up to the time, when the day begins to decline (i.e. offer Zuhr prayer). (Ibn ‘Abbâs said: "These are the five compulsory congregational prayers mentioned in the Qur’ân)." [Tafsir At-Tabari]
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.