{"references": ["Adibekyan, V. Zh., Sousa, S. G., Santos, N. C. et al. 2012, \\aap, 545, A32", "Affer, L., Micela, G., Favata, F. et al. 2013, \\mnras, 430, 1433", "Barnes, S. A. 2003, \\apj, 586, 464", "Barnes, S. A., Weingrill, J., Fritzweski, D., et al. 2016, \\apj, 823, 16", "Booth, R. S., Poppenhaeger, K., Watson, C. A. et al. 2020, \\mnras, 491, 455", "Brewer, L.N., Sandquist, E.L., Mathieu, R.D., et al. 2016, \\apj, 151, 66", "Corsaro, E., Mathur, S., Garcia, R. A. et al. 2017, \\aap, 605, A3", "Curtis, J. L., Agueros, M. A., Douglas, S. T. et al. 2019, \\apj, 879, 4", "Delorme, P., Collier Cameron, A., Hebb, L. et al. 2011, \\mnras, 413, 221", "Denissenkov, P. A., Pinsonneault, M., Terndrup, D.M., \\& Newsham, G. 2010, \\apj, 716, 1269", "Durney, B. R., Latour, J. 1978, Geophys. and Astrophys. Fluid Dyn., 9, 241", "Fritzewski D. J. , Barnes S.A., James D.J., \\& Strassmeier K. G. 2020, \\aap, 641, A51", "Gondoin, P. 2017, \\aap, 599, A122", "Gondoin, P. 2018, \\aap, 616, A154", "Gondoin, P. 2020a, \\an, 341, Issue 5, pp. 557-566", "Gondoin, P. 2020b, \\aap, 641, A110", "Hall, J.C. 2008, Living Rev. Solar Phys., 5, 2", "Hartman, J. D., Bakos, G. \u00c1., Kov\u00e1cs, G., \\& Noyes, R. W. 2010, \\mnras, 408, 475", "Irwin, J., Aigrain, S., Bouvier, J. et al. 2009, \\mnras, 392, 1456", "Lachaume, R., Dominik, C., Lanz, T. et al. 1999, \\aap, 348, 897", "Landin, N. R., Mendes, L. T. S., \\& Vaz, L. P. R. 2010, \\aap, 510, A46", "Liu, F., Asplund, M., Yong, D. et al. 2019, \\aap, 627, A117", "Lorenzo-Oliveira, D., Porto de Mello, G. F., \\& Schiavon, R. P. 2016, \\aap, 594, L3", "Lorenzo-Oliveira, D., Freitas, F. C., Melendez, J. et al. 2018, \\aap, 619, A73", "MacGregor, K. B., \\& Charbonneau, P. 1995, Cool Stars; Stellar Systems; and the Sun; Eighth Cambridge Workshop. Astronomical Society of the Pacific Conference Series, Vol. 64, p.174", "Mamajek, E. E., \\& Hillenbrand, L. A. 2008, \\apj, 687, 1264", "Mangeney, A., \\& Praderie, F. 1984, \\aap, 130, 143", "Mayor, M., \\& Martinet, L. 1977, \\aap, 55, 221", "Meibom, S., Barnes, S. A., Latham, D. W. et al. 2011, \\apj, 733, L9", "Meibom, S., Barnes, S.A.., Platais, I. et al. 2015, Nature, 517, 589", "Noyes, R. W., Hartmann, L. W., Baliunas, S. L. et al. 1984, \\apj, 279, 763", "Pace, G. 2013, \\aap, 551, L8", "Pallavicini, R., Golub, L., Rosner, R., et al. 1981, \\apj, 248, 27", "Perez Martinez, M. I., Schroder, K.-P., \\& Hauschildt 2014, \\mnras, 445, 270", "Pizzolato, N., Maggio, A., Micela, G., Sciortino, S., \\& Ventura, P. 2003, \\aap, 397, 147", "Radick, R. R., Lockwood, G. W., Skif, B.A., \\& Baliunas, S. L. 1998, \\apjs, 118, 239", "Reiners, A. \\& Mohanty S. 2012, \\apj, 746, 43", "Sandquist, E.L., Jessen-Hansen, J., Shetrone, M.D. et al. 2016, \\apj, 831, 11", "Schrijver, C. J. 1987, \\aap, 172, 111", "Skumanich, A. 1965, \\aj, 70, 692", "Soderblom, D. R., Duncan, D. K., \\& Johnson, D. R. H. 1991, \\apj, 375, 722", "Spada, F., \\& Lanzafame A. C. 2020, \\aap, 636, A76", "VandenBerg, D.A., Don, A., \\& Stetson, P.B. 2004, \\pasp, 116, 997", "Wielen, R. 1974 in Highlights of Astronomy, Vol. 3, G. Gontopoulos and G. Gontopoulos, eds. (Dordrecht: Reidel), p. 395", "Wright, N. J., Drake, J. J., Mamajek, E. E., \\& Henry, G. W. 2011, \\apj, 743, 48", "Zhang, J., Zhao, Oswalt, T. D. et al. 2019, \\apj, 887, 84"]}

The emission reversal in the cores of the CaII H and K lines of late-type dwarfs is correlated with their age and is potentially an accurate age indicator. Recent measurements of stellar rotation periods in intermediate-age open clusters indicate that the rotation rates of Sun-like stars older than 1 Gyr decay as age^{0.49M-1.19} for stellar masses M included between 0.7 and 1.1 MSun. The corresponding evolution of the R'HK activity index inferred from rotation-activity relationships is steeper than the relationship R' HK ~ age^{-0.5} generally used. Such a steep decay of the chromospheric activity beyond the age of 1 Gyr is supported by measurements of the R'HK index distributions among nearby G and K main sequence stars with near solar metallicity.